Image processing apparatus, image processing method, and program product

ABSTRACT

A transformation rule of color transformation in an appropriate color space is set even without advanced knowledge and know-how. A three-dimensional lookup table unit transforms color information on an input image signal on the basis of a transformation rule. A correction range calculation unit calculates a correction range in a predetermined color space on the basis of a positional relationship between source coordinates and destination coordinates in the color space. A lattice point transfer distance calculation unit calculates the transformation destination coordinates at respective points on the basis of the positional relationship between the source coordinates and the destination coordinates, and a positional relationship between coordinates at the respective points within the correction range and the source coordinates to reflect the calculated transformation destination coordinates on the transformation rule.

CROSS-REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application No. 2011-250926 filed onNov. 16, 2011 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to an image processing apparatus, an imageprocessing method, and a program product.

An object or a background has a specific color such as blue of blue skyor pink of cherry blossoms, with which a person images the object or thebackground. Those colors are called “memory colors”. Even if the personlooks at an image that faithfully reproduces the color of a certainobject or background in keeping with a real world, the person does notevaluate the image as being beautiful. This is because the color (memorycolor) imaged by the person is different from the reproduced color, andthe person recognizes that the color is light, or the like.

For that reason, most of the image processing apparatuses conductcorrection processing for reproducing the color imaged by the person foreach of the objects and the backgrounds. The correction processing iscalled “memory color correction”. In general, the methods ofimplementing the memory color correction include the following twomethods. That is, there are (1) a dedicated circuit (characteristiccorrection function) and (2) a three-dimensional lookup table.

First, (1) the memory color correction using the dedicated circuit willbe described. In this example, the dedicated circuit conducts processingfor specializing in the memory color correction. More specifically, aspecific color to be corrected is set for the dedicated circuit in acoordinate format of a source and a destination in a color space such asCb/Cr or a*/b*. The dedicated circuit corrects a color region includinga surrounding color region according to the setting. However, since thededicated circuit specializes in the memory color correction, thededicated circuit cannot conduct another processing. Further, in thecase of correcting the characteristics of two or more regions, aplurality of dedicated circuits are required.

Subsequently, (2) the memory color correction using a three-dimensionallookup table will be described. Information of the three-dimensionallookup table is stored in an arbitrary memory. In the three-dimensionallookup table is stored table data corresponding to coordinate pointssuch as 9×9×9 or 17×17×17 mainly expressing three-dimensional colorspaces of RGB. The three-dimensional lookup table stores correspondenceof coordinates of the respective points and coordinates of thetransformation destination of the coordinates. For example, if thethree-dimensional lookup table has the table data corresponding to thecoordinate points of 17×17×17, RGB coordinates (0, 0, 0) and RGBcoordinates of its transformation destination, and RGB coordinates (16,16, 16) and RGB coordinates of its transformation destination are storedin the three-dimensional lookup table. Then, an arbitrary processingunit refers to the three-dimensional lookup table, and transfers therespective coordinates existing in the color space to the coordinates ofthe transformation destination through a variety of interpolationprocessing. For example, the processing unit calculates thetransformation destination coordinates of the RGB coordinates (8, 8, 8)with reference to the transformation destination coordinates of the RGBcoordinates (0, 0, 0) and the transformation destination coordinates ofthe RGB coordinates (16, 16, 16).

The three-dimensional lookup table merely holds a transformation rule,and the three-dimensional lookup table per se is not provided with anyfunction. However, appropriate table data is set for thethree-dimensional lookup table, and processing is conducted according tothe transformation rule within the table, thereby making it possible torealize a variety of color management functions such as color gamutmapping, 6-axis correction, memory color correction, or gammacorrection. In this example, the table data set in the three-dimensionallookup table can be appropriately changed. For that reason, with onlythe provision of a single processing circuit (or a processing functionusing software), a necessary function (including the simultaneousrealization of a plurality of region processes and a plurality of otherfunctions) can be realized as the situation demands.

Thus, the correction using the three-dimensional lookup table has thedegree of freedom absolutely higher than that of the correction usingthe dedicated circuit function (characteristic correction function). Forthat reason, with the configuration using the three-dimensional lookuptable, a large number of advantages from the viewpoint of the costs,such as a reduction in development resource and a reduction in circuitscale, and an improvement in usability can be conducted. Furthermore,when a trouble occurs, or when the performance is improved, the tabledata in the three-dimensional lookup table is replaced with another, asa result of which the problem can be solved without changing thehardware.

Hereinafter, a description will be given of publications disclosing animage processing technology related to the above items. JapaneseUnexamined Patent Publication No. 2010-118881 discloses a color signalprocessing system that conducts color management processing on an inputmoving image with the use of the three-dimensional lookup table. Thesystem includes a color transformation unit that transforms colorinformation on an input image signal by a multidimensional lookup table,an interpolation unit that outputs a composite image signal in which theimage signal transformed by the color transformation unit is combinedwith the input image signal at an arbitrary ratio, and a lookup tablerewrite unit that changes data of the multidimensional lookup table inthe color transformation unit. With the above configuration, the systemcan realize the color management processing with high precision evenwhen rewriting data in the lookup table.

International Publication No. WO2004/032524 discloses an imageprocessing apparatus that conducts automatic color adjustment with fewadverse effects to the memory color correction. The image processingapparatus includes an intensity determination unit that generates acorrection intensity which in a periphery of a color region is smallerthan that in the color region of a specific range set on the basis oftwo chromaticity components (a*/b*), and a unit that conducts correctionaccording to the generated correction intensity.

SUMMARY

However, the correction processing in the color space in conformity withthe transformation rule such as the three-dimensional lookup tablesuffers from such a problem that an advanced knowledge and know-how forsetting the transformation rule including the memory color correctionare required. The problem will be described below.

The correction processing system using the three-dimensional lookuptable generally includes only a memory that stores the table datatherein, and a circuit that calculates a transformed value from thetable data. For that reason, the degree of freedom for setting the tabledata in the three-dimensional lookup table is very high. In the settingof the table data in the three-dimensional lookup table, there is a needto set a correction range of a color existing in the periphery of thetarget color, and the transformation destination coordinates of therespective colors within the correction range, in addition to setting ofa color (target color) to be subjected to the memory color correction,and the transformation destination of the color. For that reason, forexample, in the case of setting the above-mentioned table data relatedto the memory color correction, a setter cannot conduct appropriatesetting unless the setter holds the advanced knowledge and know-how forthe memory color correction.

If the setter sets the table data without holding satisfactory knowledgeor know-how to correct the memory color, there is a risk that a spatialdistortion may occur in the corrected image without ensuring continuitywithin the three-dimensional color space. When an image having a gentlegradation of color or brightness is input to an image processingapparatus having the above table data, there is a risk that the imageprocessing apparatus may unavoidably output an image having an outlinewhich does not originally exist, or an image having a degraded gradationcharacteristic.

Both of the image correcting techniques disclosed in Japanese UnexaminedPatent Publication No. 2010-118881 and International Publication No.WO2004/032524 assume that the setter sequentially sets the table data.For that reason, if the setter does not have the satisfactory know-howand knowledge related to the color correction, there is a risk that thesetter may not conduct an intended correction.

As described above, when the memory color correction is conducted withreference to the three-dimensional lookup table, the problem occurs ifthe setter of the lookup table has no satisfactory know-how andknowledge. However, the above problem occurs not only in the correctionusing the three-dimensional lookup table, but also in the setting of anarbitrary transformation rule required when conducting the colorcorrection in the color space. Further, the problem is not limited tothe correction intended for the memory color correction, but common to acase of conducting correction (coordinate transfer in the color space)of the pixel data included in an image.

That is, in the case of conducting the correction (coordinate transferin the color space) of the pixel data (pixel value) included in theimage, in order to calculate the correction range (range of thecoordinate points where transfer occurs) that meets a desired correctionpurpose, and set the transfer distance and direction of the respectivecoordinate points for transfer, the advanced knowledge is required. Whenthe user has the advanced knowledge, there arises such a problem thatappropriate setting is not conducted.

According to one aspect of the present invention, there is provided animage processing apparatus including: a transformation unit thattransforms color information on an input image signal on the basis of atransformation rule; a correction range calculation unit that calculatesa correction range in a predetermined color space on the basis of apositional relationship between source coordinates and destinationcoordinates in the color space; and a point-based transfer distancecalculation unit that calculates the transformation destinationcoordinates at respective points on the basis of the positionalrelationship between the source coordinates and the destinationcoordinates, and a positional relationship between coordinates at therespective points within the correction range and the source coordinatesto reflect the calculated transformation destination coordinates on thetransformation rule.

According to another aspect of the present invention, there is providedan image processing method of transforming color information on an inputimage signal on the basis of a transformation rule, including:calculating a correction range in a predetermined color space on thebasis of a positional relationship between source coordinates anddestination coordinates in the color space; and calculating thetransformation destination coordinates at respective points on the basisof the positional relationship between the source coordinates and thedestination coordinates, and a positional relationship betweencoordinates at the respective points within the correction range and thesource coordinates to reflect the calculated transformation destinationcoordinates on the transformation rule.

According to still another aspect of the present invention, there isprovided an image processing program causing a computer to execute,including: transforming color information on an input image signal onthe basis of a transformation rule; calculating a correction range in apredetermined color space on the basis of a positional relationshipbetween source coordinates and destination coordinates in the colorspace; and calculating the transformation destination coordinates atrespective points on the basis of the positional relationship betweenthe source coordinates and the destination coordinates, and a positionalrelationship between coordinates at the respective points within thecorrection range and the source coordinates to reflect the calculatedtransformation destination coordinates on the transformation rule.

In the present invention, the correction range calculation unitautomatically calculates the correction range according to thepositional relationship between the source coordinates and thedestination coordinates. Further, the point-based transfer distancecalculation unit calculates the transformation destination coordinatesat the respective lattice points within the correction range accordingto the positional relationship between the source coordinates and thedestination coordinates, and the positional relationship between thecoordinates at the respective points within the correction range and thesource coordinates to reflect the calculated transformation destinationcoordinates on the transformation rule (the three-dimensional lookuptable in this embodiment). In this case, a user has only to provide theinformation on the source coordinates and the destination coordinates.As a result, the user can realize the correction processing in the colorspace without having the knowledge related to the setting of thecorrection range and the knowledge related to the transfer distances ofthe respective points.

According to the present invention, there can be provided the imageprocessing apparatus, the image processing method, and the imageprocessing program which can calculate the correction range (range ofthe coordinate points where transfer occurs) that meets the desiredcorrection purpose, and set the transfer distance and direction of therespective coordinate points for transfer, without requiring theadvanced knowledge, in the case of conducting the correction (coordinatetransfer in the color space) of the pixel data (pixel value) included inthe image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of an imageprocessing apparatus according to a first embodiment of the presentinvention;

FIG. 2 is a block diagram illustrating a configuration of a table datageneration unit according to the first embodiment of the presentinvention;

FIG. 3 is a block diagram illustrating a configuration of a correctionrange calculation unit according to the first embodiment of the presentinvention;

FIGS. 4A and 4B are diagrams illustrating a concept of a distancebetween source coordinates and destination coordinates in a color space(GB cross-section);

FIG. 5 is a diagram illustrating a concept of rotation of a correctionrange by a correction range calculation unit according to the firstembodiment of the present invention;

FIG. 6 is a diagram three-dimensionally illustrating a relationship ofthe source coordinates, the destination coordinates, and an oval sphereindicative of the correction range;

FIG. 7 is a block diagram illustrating a configuration of a latticepoint transfer distance calculation unit according to the firstembodiment of the present invention;

FIG. 8 is a graph illustrating a relationship between the degree ofinfluence and transfer distance characteristics;

FIGS. 9A and 9B are diagrams illustrating a concept of a correctiondirection in the color space;

FIGS. 10A and 10B are conceptual diagrams illustrating the effect ofrotation of the correction range;

FIGS. 11A and 11B are conceptual diagrams illustrating a memory colorcorrection of flesh color;

FIG. 12 is a block diagram illustrating a configuration of an imageprocessing apparatus according to a second embodiment of the presentinvention;

FIG. 13 is a diagram illustrating analysis of histogram of an overallimage by a histogram analysis unit according to the second embodiment ofthe present invention;

FIG. 14 is a conceptual diagram illustrating an interference of thecorrection range;

FIGS. 15A and 15B are conceptual diagrams illustrating memory colorcorrections in the image processing apparatus according to the first andsecond embodiments of the present invention;

FIG. 16 is a block diagram illustrating a configuration of a correctionrange calculation unit according to a third embodiment of the presentinvention;

FIGS. 17A and 17B are diagrams illustrating a concept of resetting forcalculating the number of lattice points included in the correctionrange, and reducing an oval sphere;

FIG. 18 is a block diagram illustrating a configuration of a correctionrange calculation unit according to a fourth embodiment of the presentinvention;

FIG. 19 is a conceptual diagram illustrating an operation image of animage processing apparatus according to the fourth embodiment of thepresent invention;

FIGS. 20A and 20B are conceptual diagrams illustrating the operationimage of the image processing apparatus according to the fourthembodiment of the present invention;

FIG. 21 is a block diagram illustrating a configuration of an imageprocessing apparatus according to a fifth embodiment of the presentinvention;

FIG. 22 is a diagram illustrating an image example to be processed bythe image processing apparatus according to the fifth embodiment;

FIG. 23 is a diagram illustrating a correction range of blue sky and acorrection range of a blue flower in a GB cross-section;

FIG. 24 is a block diagram illustrating a configuration of a color spacetransformation unit according to a sixth embodiment of the presentinvention; and

FIG. 25 is a diagram illustrating an example of a hardware configurationwhich executes processing of the respective processing units in theimage processing apparatus as a program.

DETAILED DESCRIPTION First Embodiment

Hereinafter, an embodiment of the present invention will be describedwith reference to the accompanying drawings. FIG. 1 is a block diagramillustrating a configuration of an image processing apparatus accordingto this embodiment.

An image processing apparatus 1 includes a table data generation unit100 and a three-dimensional lookup table unit 200. The three-dimensionallookup table unit 200 includes an address generation unit 210, a tabledata memory unit 220, and an interpolation unit 230.

The three-dimensional lookup table unit 200 holds a three-dimensionallookup table, and transforms an input RGB signal. The three-dimensionallookup table unit 200 conducts a general memory color correction withthe use of the three-dimensional lookup table. In this example, thethree-dimensional lookup table held by the three-dimensional lookuptable unit 200 is a three-dimensional lookup table in a general RGBspace having lattice points such as 9×9×9 or 17×17×17 with a precisionof 8 bits or 10 bits. The three-dimensional lookup table unit 200 holdscorrespondence relationships of the same number as that of the latticepoints such as to allow lattice point coordinates (R1, G1, B1) in theRGB space to transfer to (R2, G2, B2). A method of interpolating thelattice points within the three-dimensional lookup table unit 200(method of calculating the destination of the coordinates in the colorspace not included in the lattice point) may use a linear interpolationmethod or a cubic interpolation method in the general three-dimensionalspace.

The memory color correction processing designates a specific colorregion within the three-dimensional color space to conduct correction.For that reason, the correction can be conducted with higher precisionas the number of lattice points is larger. For that reason, eightlattice points in the three-dimensional lookup table should be thenumber of lattice points of 9×9×9 or more. With this configuration, thememory color correction sustainable in real use can be implemented.

Subsequently, a description will be given of a configuration of thetable data generation unit 100 with reference to FIG. 2. The table datageneration unit 100 includes a correction range calculation unit 110 anda lattice point transfer distance calculation unit 120. The user inputs,to the table data generation unit 100, three set values including sourcecoordinates (coordinate points on the RGB coordinates) of a color to besubjected to the memory color correction, destination coordinates(coordinate points on the RGB coordinates), and a correction direction(compression direction/parallel direction). The user may further setinfluence range gain and offset, and transfer characteristics. If nosetting is conducted, a default value may be used. Likewise, if nocorrection direction is set, a default value (for example, compressiondirection) may be used.

The correction range calculation unit 110 is a processing unit forcalculating a range (correction range) in the color space in which thememory color correction is conducted on the basis of the above-mentionedthree set values (the source coordinates, the destination coordinates,and the correction direction). If the user feels that the correctionrange calculated by the correction range calculation unit 110 isimproper (too wide, too narrow), the user can adjust the influence rangegain and offset to adjust the correction range. The details will bedescribed later.

The correction range calculation unit 110 supplies the calculatedcorrection range (a range in which the coordinates in the color spaceare changed with the memory color correction) to the lattice pointtransfer distance calculation unit 120. The lattice point transferdistance calculation unit 120 automatically calculates the transferdistances of the respective lattice points within the correction range,and generates the table data of the three-dimensional lookup table onthe basis of the transfer distance.

In detail, the lattice point transfer distance calculation unit 120calculates the degree of influence (an index value of the transferdistance of each lattice point, which will be described in detail later)on the basis of a distance between the source coordinates which is acenter of the transfer and the coordinates at each lattice point. Thedegree of influence calculated from the lattice point closer to thesource coordinates becomes larger. The degree of influence calculatedfrom the lattice point longer in the distance from the sourcecoordinates becomes smaller. The degree of influence calculated from thelattice point outside the influence range (outside the correction range)becomes 0.

The lattice point transfer distance calculation unit 120 calculates thedegree of influence at each of the lattice points, and calculates thetransfer distance of each lattice point according to the degree ofinfluence. The lattice point transfer distance calculation unit 120 addsthe transfer distance calculated for each of the lattice points to thecoordinate value at each of the lattice points to generate the tabledata.

If the user intends to adjust the transfer distance calculated from thedegree of influence, the user may adjust an input value of the transfercharacteristics. The details of the transfer characteristics will bedescribed later.

Subsequently, a significance of calculating the correction range and thetransfer distance of each lattice point will be described on the basisof the above input (the source coordinates, the destination coordinates)prior to description of the detailed configurations and operations ofthe correction range calculation unit 110 and the lattice point transferdistance calculation unit 120.

In the image processing apparatus 1 according to this embodiment, whenthe user conducts the memory color correction, the user sets the colorcoordinates of the source which is the center of the transfer, and setsthe color coordinates of the destination indicative of how the color iscolored. Upon receiving the setting, the correction range calculationunit 110 calculates the correction range. That is, the correction rangecalculation unit 110 also selects colors (coordinates) existing aroundthe set two color coordinates as the transfer target. The two reasonsfor the above selection will be described below.

The first reason is because the continuity within the three-dimensionalcolor space is ensured to prevent a spatial distortion so that thegradation characteristics are not deteriorated.

The second reason is because the color to be corrected is notconcentrated in a certain point in the three-dimensional space, butrequires correction to a certain color region. For example, this isbecause when the memory color correction of blue is conducted, blue tobe corrected is not concentrated in a certain point in thethree-dimensional space, but a given color region around that point isto be corrected.

In general, for example, when the color region of the flesh color to besubjected to the memory color correction is set, sample data of theflesh color existing in the world is acquired. Then, statistical data ofa preferable flesh color is collected aside from the acquired data. Inaddition, those data is analyzed by using the advanced know-how todetermine which flesh color is set as the center (the sourcecoordinates), what range (correction range) is defined as the fleshcolor, and which color is set as a preferable flesh color (thedestination).

However, just the flesh color still refers to a variety of races. Forthat reason, when all of the flesh color regions are defined, theregions become remarkably widened. Further, a change in the flesh colordue to a light source of photographing environments, and a change in howto see the flesh color due to a background color also occur. For thatreason, it is impossible to conduct absolutely preferable setting in anycases. Further, there are many cases in which the memory colors areoriginally ambiguously defined. For that reason, the memory colors maybe largely different depending on the user's leaning or the regionality.In summary, it is frequently very difficult to set the sourcecoordinates and the destination coordinates to be subjected to thecorrection of the memory color. However, it is also a fact that when thecolor of an image is corrected to a tendency of the preferred color andbrightness, a certain amount of correction effect is obtained.

Hence, in the image processing apparatus according to this embodiment,if each user sets “correction is intended to be conducted to approachthis color with a focus on this color” (that is, sets the coordinates ofthe above-mentioned source and destination), the correction rangecalculation unit 110 automatically calculates the correction range.Also, the lattice point transfer distance calculation unit 120automatically calculates the transfer distance of each lattice pointwithin the correction range. As a result, in the image processingapparatus 1 according to this embodiment, there can be easily provided aunit for correcting the memory color with no problem real-operationallyeven if the user does not hold the above-mentioned statistical data andthe advanced adjustment know-how.

Subsequently, a description will be given of a detailed configuration ofthe correction range calculation unit 110 with reference to FIG. 3. FIG.3 is a block diagram illustrating a configuration of the correctionrange calculation unit 110. The correction range calculation unit 110includes a destination to source distance calculation unit 111, acorrection range gain and offset adjustment unit 112, a destination tosource line inclination calculation unit 113, a rotation anglecalculation unit 114, and a correction range oval sphere expressioncalculation unit 115. FIGS. 4A to 6 are diagrams illustrating the sourcecoordinates, the destination coordinates, and the correction range inthe color space. Hereinafter, those drawings will be appropriatelyreferred to for description.

The destination to source distance calculation unit 111 receives thesource coordinates and destination coordinates set by the user. Thedestination to source distance calculation unit 111 subtracts the sourcecoordinates from the destination coordinates to calculate a distancebetween the destination coordinates and the source coordinates in thecolor space. The source coordinates, the destination coordinates, andthe distance from the destination coordinates to the source coordinatesare defined as follows to represent formulae for computation. Sourcecoordinates: O (Ro, Go, Bo), Destination coordinates: T (Rt, Gt, Bt),source to destination distance: Lto (Rlto, Glto, Blto) Lto=(Rt-Ro,Gt-Go, Bt-Bo).

FIGS. 4A and 4B illustrate a concept of a distance Lto between thesource coordinates and the destination coordinates in the color space(GB cross-section). In FIGS. 4A and 4B, for limitation of the drawings,two-dimensional cross-sections are illustrated, but the destination tosource distance calculation unit 111 calculates the distance in thethree-dimensional space.

The destination to source distance calculation unit 111 supplies thecalculated source to destination distance (Lto) to the correction rangegain and offset adjustment unit 112.

The correction range gain and offset adjustment unit 112 determines thecorrection range for each axis of the respective RGB on the basis of thesupplied source to destination distance (Lto). A correction range gainand a correction range offset are appropriately set by the user. When nosetting is conducted, default values are used. Hereinafter, a correctionrange E, a correction range gain Egain, and a correction range offsetEofs are defined to express Formulae for computation (Ex. 1) to (Ex. 3)used by the correction range gain and offset adjustment unit 112.Correction range: E (Re, Ge, Be), Correction range gain: Egain, andCorrection range offset: EofsRe=Rlto×Egain+Eofs  (Ex. 1)Ge=Glto×Egain+Eofs  (Ex. 2)Be=Blto×Egain+Eofs  (Ex. 3)

It is assumed that the correction range gain Egain can be adjustedbetween “1” and “5” by the user, but is set to about “3”. It is assumedthat the correction range offset Eofs can be adjusted between “8” and“64” by the user in the case of 8-bit (256) gradations, but is set toabout “16”.

The user can adjust the correction range gain Egain and the correctionrange offset Eofs to automatically set the magnitude of the correctionrange E according to the distance Lto between the source coordinates andthe destination coordinates. The range of the correction range E iswider as the correction range gain Egain and the correction range offsetEofs are larger (oval sphere range becomes larger in FIGS. 4A and 4B).Because the correction range gain Egain is not a value of 1 or lower,the source coordinates and the destination coordinates are includedwithin the correction range E in principle. The correction range gainand offset adjustment unit 112 supplies the calculated correction rangeE to the correction range oval sphere expression calculation unit 115.

The destination to source line inclination calculation unit 113calculates an inclination (Δrg) of the RG cross-section and aninclination (Δgb) of the GB cross-section according to the sourcecoordinates and the destination coordinates. In more detail, thedestination to source line inclination calculation unit 113 calculatesthe inclination (Δrg) of the RG cross-section according to positionalrelationships of an R coordinate (Ro) and a G coordinate (Go) of thesource coordinates, and an R coordinate (Rt) and a G coordinate (Gt) ofthe destination coordinates. Likewise, the destination to source lineinclination calculation unit 113 calculates the inclination (Δgb) of theGB cross-section according to positional relationships of the Gcoordinate (Go) and a B coordinate (Bo) of the source coordinates, andthe G coordinate (Gt) and a B coordinate (Bt) of the destinationcoordinates. In more detail, the destination to source line inclinationcalculation unit 113 calculates the inclination (Δrg) of the RGcross-section and the inclination (Δgb) of the GB cross-section with theuse of the following formulae for computation (Ex. 4) and (Ex. 5).

$\begin{matrix}{{\Delta\;{rg}} = \frac{{Gt} - {Go}}{{Rt} - {Ro}}} & ( {{Ex}.\mspace{14mu} 4} ) \\{{\Delta\;{gb}} = \frac{{Bt} - {Bo}}{{Gt} - {Go}}} & ( {{Ex}.\mspace{14mu} 5} )\end{matrix}$

The destination to source line inclination calculation unit 113 suppliesthe calculated inclination (Δrg) of the RG cross-section and thecalculated inclination (Δgb) of the GB cross-section to the rotationangle calculation unit 114. FIG. 4A illustrates the inclination (Δgb) ofthe GB cross-section.

The rotation angle calculation unit 114 calculates an angle (θrg, θgb)by which an oval sphere configured by an outer periphery of thecorrection range E rotates, according to the supplied inclination (Δrg)of the RG cross-section and the supplied inclination (Δgb) of the GBcross-section. In more detail, the rotation angle calculation unit 114calculates the rotation angle (θrg, θgb) with the use of the followingformulae for computation (Ex. 6) and (Ex. 7).

$\begin{matrix}{{{\theta\;{rg}} = {\frac{a\;{\tan( {\Delta\;{rg}} )} \times 180}{\pi}({^\circ})}},{{{Rt} - {Ro}} = {0\mspace{14mu}\mspace{14mu} 90({^\circ})}}} & ( {{Ex}.\mspace{14mu} 6} ) \\{{{\theta\;{gb}} = {\frac{a\;{\tan( {\Delta\;{gb}} )} \times 180}{\pi}({^\circ})}},{{{Gt} - {Go}} = {0\mspace{14mu}\mspace{14mu} 0({^\circ})}}} & ( {{Ex}.\mspace{14mu} 7} )\end{matrix}$

The correction range oval sphere expression calculation unit 115 is aprocessing unit that calculates an oval sphere expression of thecorrection range. The correction range oval sphere expressioncalculation unit 115 axially rotates the oval sphere configured by theouter periphery of the correction range E calculated by the correctionrange gain and offset adjustment unit 112 by the angle (θrg, θgb)calculated by the rotation angle calculation unit 114 about therespective axes to calculate the oval sphere expression of a finalcorrection range E. In more detail, the correction range oval sphereexpression calculation unit 115 rotates a coordinate variable (R0, G0,B0) about an RG axis with the aid of the following expression (Ex. 8) tocalculate coordinates (R1, G1, *). The correction range oval sphereexpression calculation unit 115 rotates the coordinates (R1, G1, *)about an RG axis with the aid of the following expression (Ex. 9) tocalculate coordinates (R1, G2, B1). The correction range oval sphereexpression calculation unit 115 calculates the formula for computation(Ex. 10) of the axially rotated oval sphere expression according to thecoordinate point (R1, G2, B1). The correction range oval sphereexpression calculation unit 115 calculates the formula for computation(Ex. 10) of the axially rotated oval sphere expression according to thecoordinate point (R1, G2, B1).

$\begin{matrix}{{{R\; 1} = {{\cos\;\theta\;{rg} \times R\; 0} - {\sin\;\theta\;{rg} \times G\; 0}}}{{G\; 1} = {{\sin\;\theta\;{rg} \times R\; 0} + {\cos\;\theta\;{rg} \times G\; 0}}}} & ( {{Ex}.\mspace{14mu} 8} ) \\{{{G\; 2} = {{\cos\;\theta\;{gb} \times G\; 1} - {\sin\;\theta\;{gb} \times B\; 0}}}{{B\; 1} = {{\sin\;\theta\;{gb} \times G\; 1} + {\cos\;\theta\;{gb} \times B\; 0}}}} & ( {{Ex}.\mspace{14mu} 9} ) \\{{\frac{R\; 1^{2}}{{Re}^{2}} + \frac{G\; 2^{2}}{G\; e^{2}} + \frac{B\; 1^{2}}{B\; e^{2}}} = 1} & ( {{Ex}.\mspace{14mu} 10} )\end{matrix}$

The correction range oval sphere expression calculation unit 115supplies the oval sphere expression of the calculated correction range Eto the lattice point transfer distance calculation unit 120(intersection point calculation unit 122).

FIG. 5 is a diagram illustrating a concept of rotation of the correctionrange E. FIG. 5 illustrates the rotation concept of the RGcross-section. As illustrated in the figure, the correction range E isrotated according to the positional relationship between the sourcecoordinates and the destination coordinates. That is, the correctionrange oval sphere expression calculation unit 115 rotates the correctionrange E so that a line connecting the source coordinates and thedestination coordinates is parallel to a long side direction of the ovalsphere.

FIG. 6 is a diagram three-dimensionally illustrating a relationship ofthe source coordinates, the destination coordinates, and the oval sphereindicative of the correction range. As illustrated in the figure, theoval sphere has the source coordinates and the destination coordinatesinside thereof.

As described above, the user sets the source coordinates and thedestination coordinates point by point. The correction range calculationunit 110 automatically calculates the correction range E through aseries of processing described above. In the above-mentioned techniquefor calculating the correction range E, a center of the oval sphereindicative of the correction range is correction source coordinates.However, the above-mentioned calculating technique is merely one exampleof the technique for calculating the oval sphere of the correction rangeE, and the center of the oval sphere may be intermediate coordinatesbetween the source coordinates and the destination coordinates, or maybe coordinates close to the source coordinates (destinationcoordinates).

Further, in the above technique for calculating the correction range E,the correction range is indicated by an oval sphere. However, theexpression representative of the correction range E does not always needto be a complicated mathematical expression such as the oval sphereexpression. The expression may be a simple mathematical expression suchas a linear expression as long as the expression represents a rangecorresponding to the above oval sphere expression (that is, a rangecalculated on the basis of the positional relationship between thesource coordinates and the destination coordinates). The correctionrange E represented by the linear expression is, for example, a regularsolid (octagon) and a cuboid (octagon, decagon, dodecagons).

Subsequently, the configuration and operation of the lattice pointtransfer distance calculation unit 120 will be described with referenceto FIG. 7. FIG. 7 is a block diagram illustrating the configuration ofthe lattice point transfer distance calculation unit 120. First, anoutline of the processing of the lattice point transfer distancecalculation unit 120 will be described.

The lattice point transfer distance calculation unit 120 calculates thetransfer distances of the respective lattice points within the ovalsphere represented by the oval sphere expression of the correction rangeE which is input from the correction range oval sphere expressioncalculation unit 115. For example, the lattice point transfer distancecalculation unit 120 calculates the transfer distances of the respectivelattice points within the correction range of FIG. 4A.

In detail, the lattice point transfer distance calculation unit 120first calculates intersection points between a line that passes throughthe source coordinates of each lattice point, and the oval sphererepresented by the input oval sphere expression. The lattice pointtransfer distance calculation unit 120 then calculates a distance(normalization distance) between the intersection point and the sourcecoordinates. The lattice point transfer distance calculation unit 120also calculates a distance between the source coordinates and thelattice point. The lattice point transfer distance calculation unit 120calculates the degree of transfer influence according to a ratio of thedistance (distance between the source coordinates and the lattice point)and the normalization distance. The lattice point transfer distancecalculation unit 120 then calculates the transfer distance of thelattice point for each of the RGB coordinates according to arelationship of the degree of influence, the source coordinates, thedestination coordinates, and the lattice point coordinates. The latticepoint transfer distance calculation unit 120 adds the transfer distancefor each of the RGB coordinates to the lattice point coordinates tocalculate the coordinates of the transferred lattice point. Thetransferred coordinates become the table data of the memory colorcorrection.

In the following description, the lattice points (coordinate arrangementwhere all of distances to the vertical and horizontal adjacent latticepoints are uniform) are dealt with. However, the present invention isnot always limited to this configuration. The lattice point transferdistance calculation unit 120 (point-based transfer distance calculationunit) may calculate the transfer distance of each coordinate pointhaving alignments other than the lattice points. In this case, thethree-dimensional lookup table unit 200 may conduct interpolationprocessing with reference to a distance relationship of the respectivecoordinate points.

Subsequently, a description will be given of the detailed configurationof the lattice point transfer distance calculation unit 120 and theoperation of the respective configuration processing units. The latticepoint transfer distance calculation unit 120 includes a source tolattice point linear expression calculation unit 121, an intersectionpoint calculation unit 122, a source coordinates to intersection pointdistance calculation unit 123, a source to lattice point linear distancecalculation unit 124, an influence degree calculation unit 125, atransfer characteristic setting unit 126, and a coordinate calculationunit 127.

The source to lattice point linear expression calculation unit 121calculates a linear expression of a line that connects the sourcecoordinates and each of the coordinates included within the correctionrange E. In this example, when arbitrary lattice point coordinates Dincluded in the correction range E, and a coordinate variable INPUT aredefined as follows, the linear expression is calculated as the followingexpression (Ex. 11) through a general three-dimensional straight-lineequation.

Lattice point coordinates: D (Rd, Gd, Bd) within the correction rangeoval sphere

Coordinate variable: (R0, G0, B0)

$\begin{matrix}{{{\frac{R\; 0}{{Rd} - {Ro}} = {\frac{G\; 0}{{Gd} - {Go}} = {\frac{B\; 0}{{Bd} - {Bo}} = 1}}},{{G\; 0} = {\frac{{Gd} - {Go}}{{Rd} - {Ro}} \times R\; 0}},{{B\; 0} = {\frac{{Bd} - {Bo}}{{Rd} - {Ro}} \times R\; 0}}}\begin{matrix}{{R\; 1^{2}} = ( {{\cos^{2}\theta\;{rg}} - {2 \times \cos\;\theta\;{rg} \times \sin\;\theta\;{rg} \times ( \frac{{Gd} - {Go}}{{Rd} - {Ro}} )} +} } \\{ {\sin^{2}\theta\;{rg} \times ( \frac{{Gd} - {Go}}{{Rd} - {Ro}} )^{2}} ) \times R\; 0^{2}} \\{= {A \times R\; 0^{2}}}\end{matrix}} & ( {{Ex}.\mspace{14mu} 11} )\end{matrix}$

The source to lattice point linear expression calculation unit 121supplies the calculated linear expression (Ex. 11) at each of thelattice points to the intersection point calculation unit 122.

The intersection point calculation unit 122 receives the oval sphereexpression (oval sphere expression after axial rotation, (Ex. 10)) ofthe correction range E which is input from the correction range ovalsphere expression calculation unit 115, and the linear expression (Ex.11) calculated from each of the lattice points. The intersection pointcalculation unit 122 calculates the intersection point between the ovalsphere (oval sphere of the correction range E) and the line (lineconnecting the source coordinates and an arbitrary lattice point) byassigning the linear expression into the oval sphere expression.Assignment expressions will be represented as follows. First, anassignment expression (Ex. 12) related to R1 is represented.

$\begin{matrix}\begin{matrix}{{R\; 1^{2}} = ( {{\cos\;\theta\;{rg} \times R\; 0} - {\sin\;\theta\;{rg} \times G\; 0}} )^{2}} \\{= {{\cos^{2}\theta\;{rg} \times R\; 0^{2}} - {2 \times \cos\;\theta\;{rg} \times R\; 0 \times \sin\;\theta\;{rg} \times}}} \\{{G\; 0} + {\sin^{2}\theta\;{rg} \times G\; 0^{2}}} \\{= {{\cos^{2}\theta\;{rg} \times R\; 0^{2}} - {2 \times \;\cos\;\theta\;{rg} \times R\; 0 \times \sin\;\theta\;{rg} \times}}} \\{{( \frac{{Gd} - {Go}}{{Rd} - {Ro}} ) \times R\; 0} + {\sin^{2}\theta\;{rg} \times ( \frac{{Gd} - {Go}}{{Rd} - {Ro}} )^{2} \times R\; 0^{2}}} \\{= ( {{\cos^{2}\theta\;{rg}} - {2 \times \cos\;\theta\;{rg} \times \sin\;\theta\;{rg} \times ( \frac{{Gd} - {Go}}{{Rd} - {Ro}} )} +} } \\{ {\sin^{2}\theta\;{rg} \times ( \frac{{Gd} - {Go}}{{Rd} - {Ro}} )^{2}} ) \times R\; 0^{2}} \\{= {A \times R\; 0^{2}}}\end{matrix} & ( {{Ex}.\mspace{14mu} 12} )\end{matrix}$

In Expression 12, a part of parts is replaced with a variable A.Likewise, an assignment expression (Ex. 13) related to G2 isrepresented. The assignment manner is identical with that of Expression12, and therefore the details of assignment processing are simplifiedfor description.

$\begin{matrix}\begin{matrix}{{G\; 2^{2}} = ( {{\cos^{2}\theta\;{gb} \times ( {{\sin\;\theta\;{rg}} + {\cos\;\theta\;{rg} \times ( \frac{{Gd} - {Go}}{{Rd} - {Ro}} )}} )^{2}} - {2 \times}} } \\{\cos\;\theta\;{gb} \times \sin\;\theta\;{gb} \times ( \frac{{Bd} - {Bo}}{{Rd} - {Ro}} ) \times ( {{\sin\;\theta\;{rg}} + {\cos\;\theta\;{rg} \times}} } \\{ { ( \frac{{Gd} - {Go}}{{Rd} - {Ro}} ) ) + {\sin^{2}\theta\;{gb} \times ( \frac{{Bd} - {Bo}}{{Rd} - {Ro}} )^{2}}} ) \times R\; 0^{2}} \\{= {B \times R\; 0^{2}}}\end{matrix} & ( {{Ex}.\mspace{14mu} 13} )\end{matrix}$

In Expression 13, a part of parts is replaced with a variable B.Likewise, an assignment expression (Ex. 14) related to B1 isrepresented. In Expression 14, a part of parts is replaced with avariable C.

$\begin{matrix}\begin{matrix}{{B\; 1^{2}} = ( {{\sin^{2}\theta\;{rg} \times ( {{\sin\;\theta\;{rg}} + {\cos\;\theta\;{rg} \times ( \frac{{Gd} - {Go}}{{Rd} - {Ro}} )}} )^{2}} +} } \\{2 \times \cos\;\theta\;{gb} \times \sin\;\theta\;{gb} \times ( \frac{{Bd} - {Bo}}{{Rd} - {Ro}} ) \times} \\{( {{\sin\;\theta\;{rg}} + {\cos\;\theta\;{rg} \times ( \frac{{Gd} - {Go}}{{Rd} - {Ro}} )}} ) + {\cos^{2}\theta\;{gb} \times}} \\{ ( \frac{{Bd} - {Bo}}{{Rd} - {Ro}} )^{2} ) \times R\; 0^{2}} \\{= {C \times R\; 0^{2}}}\end{matrix} & ( {{Ex}.\mspace{14mu} 14} )\end{matrix}$

Through the above expressions, an intersection point Cr can be found bythe following expression (Ex. 15). Intersection point Cr (Rcr, Gcr, Bcr)

$\begin{matrix}{R_{CF} = \frac{{Re} \times {Ge} \times {Be}}{\sqrt{{{Ge}^{2} \times {Be}^{2} \times A} + {{Re}^{2} \times {Be}^{2} \times B} + {{Re}^{2} \times {Ge}^{2} \times C}}}} & ( {{Ex}.\mspace{14mu} 15} )\end{matrix}$

Also, in the case of Rd=Ro, division by zero occurs in the linearexpression (Ex. 11). Hence, the above-mentioned Rcr and B0 arerepresented by the following expression (Ex. 16).

$\begin{matrix}{{{Rcr} = 0},{{B\; 0} = {\frac{{Bd} - {Bo}}{{Gd} - {G\; 0}} \times G\; 0}}} & ( {{Ex}.\mspace{14mu} 16} )\end{matrix}$

When Expression 16 is assigned into the oval sphere expression (Ex. 10),the following expressions (Ex. 17) to (Ex. 19) are obtained.

$\begin{matrix}{\mspace{79mu}{{R\; 1^{2}} = {{\sin^{2}\theta\;{rg} \times G\; 0^{2}} = {A \times G\; 0^{2}}}}} & ( {{Ex}.\mspace{14mu} 17} ) \\{{G\; 2^{2}} = {{( {{\cos^{2}\theta\;{gb} \times \cos^{2}\theta\;{rg}} - {2 \times \cos\;\theta\;{gb} \times \sin\;\theta\;{gb} \times \cos\;\theta\;{rg} \times ( \frac{{Bd} - {Bo}}{{Gd} - {Go}} )} + {\sin^{2}\theta\;{gb} \times ( \frac{{Bd} - {Bo}}{{Gd} - {Go}} )^{2}}} ) \times G\; 0^{2}} = {B \times G\; 0^{2}}}} & ( {{Ex}.\mspace{14mu} 18} ) \\{{B\; 1^{2}} = {{( {{\sin^{2}\theta\;{gb} \times \cos^{2}\theta\;{rg}} + {2 \times \sin\;\theta\;{gb} \times \cos\;\theta\;{gb} \times \cos\;\theta\;{rg} \times ( \frac{{Bd} - {Bo}}{{Gd} - {Go}} )} + {\cos^{2}\theta\;{gb} \times ( \frac{{Bd} - {Bo}}{{Gd} - {Go}} )^{2}}} ) \times G\; 0^{2}} = {C \times G\; 0^{2}}}} & ( {{Ex}.\mspace{14mu} 19} )\end{matrix}$

Through the above Expressions 17 to 19, the intersection point Cr can befound by the following expression (Ex. 20).

$\begin{matrix}{{{Gcr} = \frac{{Re} \times {Ge} \times {Be}}{\sqrt{{{Ge}^{2} \times {Be}^{2} \times A} + {{Re}^{2} \times {Be}^{2} \times B} + {{Re}^{2} \times {Ge}^{2} \times C}}}}\mspace{20mu}{{{Rcr} = 0},\mspace{20mu}{{Bcr} = {\frac{{Bd} - {Bo}}{{Gd} - {Go}} \times {Gcr}}}}} & ( {{Ex}.\mspace{14mu} 20} )\end{matrix}$

Also, in the case of Gd=Go, division by zero occurs in the linearexpression (Ex. 11). Hence, the above-mentioned Rcr and Bcr arerepresented by the following expression (Ex. 21).Rcr=Gcr=0  (Ex. 21)

When Expression 21 is assigned into the oval sphere expression (Ex. 10),the following expressions (Ex. 22) to (Ex. 24) can be obtained.R1² =A×G0²(A=0)  (Ex. 22)G2²=sin² θgb×B0² =B×B0²  (Ex. 23)B1²=cos² θgb×B0² =C×B0²  (Ex. 24)

Through the above Expressions 22 to 24, the intersection point Cr can befound by the following expression (Ex. 25).

$\begin{matrix}{{{Bcr} = {\frac{{Re} \times {Ge} \times {Be}}{\sqrt{{{Ge}^{2} \times {Be}^{2} \times A} + {{Re}^{2} \times {Be}^{2} \times B} + {{Re}^{2} \times {Ge}^{2} \times C}}} = \frac{{Re} \times {Ge} \times {Be}}{\sqrt{{{Re}^{2} \times {Be}^{2} \times \sin^{2}\theta\;{gb}} + {{Re}^{2} \times {Ge}^{2} \times \cos^{2}\theta\;{gb}}}}}},\mspace{20mu}{{Rcr} = {{Gcr} = 0}}} & ( {{Ex}.\mspace{14mu} 25} )\end{matrix}$

As described above, the intersection point calculation unit 122calculates the intersection point Cr corresponding to each of thelattice points. The intersection point calculation unit 122 supplies thecoordinates of the calculated intersection point Cr (the intersectionpoint between the oval sphere and the line connecting the lattice pointand the source coordinates) corresponding to each of the calculatedlattice points to the source coordinates to intersection point distancecalculation unit 123.

The source coordinates to intersection point distance calculation unit123 calculates a distance Loc between the source coordinates and thecoordinates of the intersection point (intersection point between theoval sphere and the line connecting the lattice point and the sourcecoordinates) corresponding to each of the lattice points. The sourcecoordinates to intersection point distance calculation unit 123calculates the distance Loc from the following expression (Ex. 26) withthe use of the Pythagorean theorem.Loc=√{square root over ((Rcr−Ro)²+(Gcr−Go)²+(Bcr−Bo)²)}{square root over((Rcr−Ro)²+(Gcr−Go)²+(Bcr−Bo)²)}{square root over((Rcr−Ro)²+(Gcr−Go)²+(Bcr−Bo)²)}  (Ex. 26)

The distance Loc represents a range in which transfer occurs centeringon the source coordinates. For that reason, it is assumed that thedistance Loc is a normalization distance in the transfer range. Thesource coordinates to intersection point distance calculation unit 123supplies the normalization distance Loc calculated for each of thelattice points to the influence degree calculation unit 125.

The source to lattice point linear distance calculation unit 124calculates a distance between the source coordinates O and an arbitrarylattice point D. The source to lattice point linear distance calculationunit 124 calculates a distance Lod from the following expression (Ex.27) with the use of the Pythagorean theorem.Lod=√{square root over ((Rd−Ro)²+(Gd−Go)²+(Bd−Bo)²)}{square root over((Rd−Ro)²+(Gd−Go)²+(Bd−Bo)²)}{square root over((Rd−Ro)²+(Gd−Go)²+(Bd−Bo)²)}  (Ex. 27)

The source to lattice point linear distance calculation unit 124supplies the normalization distance Lod calculated for each of thelattice points to the influence degree calculation unit 125. FIG. 4B isa diagram illustrating a relationship between the normalization distanceLoc and the distance Lod.

The influence degree calculation unit 125 calculates the degree ofinfluence Ef used to calculate the transfer distance for each of thelattice points. The influence degree calculation unit 125 receives theabove-mentioned normalization distance Loc and distance Lod for each ofthe lattice points. The transfer distance for each of the lattice pointsbecomes larger as the degree of influence Ef is larger. The degree ofinfluence Ef becomes maximum when being calculated from the vicinity ofthe source coordinates, and the intersection point Cr becomes 0 (a valueat which there is no transfer). This is because the source coordinatesbecome the center of transfer. The influence degree calculation unit 125calculates the degree of influence Ef by the following Expression 28.

$\begin{matrix}{{Ef} = {1 - \frac{Lod}{Loc}}} & ( {{Ex}.\mspace{14mu} 28} )\end{matrix}$

The influence degree calculation unit 125 calculates the above-mentioneddegree of influence Ef for each of the lattice points in the correctionrange E.

As a result, the transfer distance of each lattice point close to thesource coordinates becomes larger, and the transfer distance becomessmaller as the lattice point is farther from the source coordinates. Thetransfer distance (the degree of influence Ef) of each lattice point onthe correction range oval sphere becomes 0. As a result, the continuitywithin the three-dimensional color space is ensured. Since thecontinuity is ensured, the memory color correction having no colordistortion can be conducted.

The influence degree calculation unit 125 supplies the calculated degreeof influence Ef for each of the lattice points to the transfercharacteristic setting unit 126.

The transfer characteristic setting unit 126 calculates transferdistance characteristics ME according to the degree of influence Ef foreach of the lattice points. The transfer distance characteristics ME area coefficient of the transfer distance for each of the lattice points.When it is assumed that the above-mentioned degree of influence Ef foreach of the lattice points is a transfer distance, the transfer distance(transfer distance characteristics ME) becomes smaller as the latticepoint is farther from the source coordinates. The transfercharacteristic setting unit 126 calculates the transfer distancecharacteristics ME, for example, from the following Expression 29according to the degree of influence Ef for each of the lattice points.ME=1−(Ef−1)²  (Ex. 29)

FIG. 8 is a graph illustrating a relationship between the degree ofinfluence Ef and transfer distance characteristics ME. The transferdistance (transfer distance characteristics ME) is controlled from theabove Expression 29 according to the degree of influence Ef. Asillustrated in FIG. 8, the above transfer distance (transfer distancecharacteristics ME) becomes large as compared with a linear change inthe degree of influence Ef. As a result, a more proper transfer distancecan be set.

If the user does not satisfy the transfer distance characteristics MEcalculated by the transfer characteristic setting unit 126, the user mayappropriately adjust the transfer distance characteristics ME. That is,the user may appropriately set a formula for computation used in thetransfer characteristic setting unit 126.

The transfer characteristic setting unit 126 supplies the calculatedtransfer distance characteristics ME for each of the lattice points tothe coordinate calculation unit 127.

The coordinate calculation unit 127 calculates the transfer distance M(Mr, Mg, Mb) for each of the lattice points on the basis of the transferdistance characteristics ME for each of the lattice points, and adds thetransfer distance M to each of the lattice point coordinates D tocalculate corrected coordinates DC(DCr, DCg, DCb) of each lattice point.The coordinate calculation unit 127 receives a correction direction inaddition to the transfer distance characteristics ME for each of thelattice points and each of the lattice point coordinates D. Thecorrection direction is designated by the user to designate one of acompression direction and a parallel direction. Hereinafter, thecorrection direction will be described with reference to FIGS. 9A and9B.

As illustrated in FIG. 9A, the compression direction is corrected tochange the coordinate position so as to concentrate on the coordinatesof one point designated by the user. As a result, even if any color isinput, the memory color is so corrected as to approach a preferablecolor (preferable coordinates). In other words, the correction is madeto narrow a color reproduction range.

As illustrated in FIG. 9B, the parallel direction is corrected totransfer all of the lattice points within the correction range in thesame direction. The transfer direction is to connect the sourcecoordinates designated by the user and the destination coordinates. Inother words, because the correction of the parallel direction transfersall of the lattice points within the correction range in the samedirection, the color reproduction range is not narrowed as compared withthe correction of the compression direction.

The user designates the correction direction according to a purpose ofthe memory color correction. The coordinate calculation unit 127calculates the transfer distance M (Mr, Mg, Mb) of each lattice pointand the corrected coordinates DC(DCr, DCg, DCb) of each lattice pointfrom the following formula for computation according to the designatedcorrection direction.

The formula for computation of the compression direction is representedby the following Expression 30.Mr=(Rt−Rd)×ME, Mg=(Gt−Gd)×ME, Mb=(Bt−Bd)×ME DCr=Rd+Mr, DCg=Gd+Mg,DCb=Bd+Mb  (Ex. 30)

The formula for computation of the parallel direction is represented bythe following Expression 31.Mr=(Rt−Ro)×ME, Mg=(Gt−Go)×ME, Mb=(Bt−Bo)×ME DCr=Rd+Mr, DCg=Gd+Mg,DCb=Bd+Mb  (Ex. 31)

The coordinate calculation unit 127 supplies the corrected coordinatesDC of each lattice point within the correction range E to the table datamemory unit 220. As a result, the table data memory unit 220 holds alookup table for transforming the arbitrary lattice point D into thecorresponding corrected coordinates DC.

Subsequently, the advantages of the image processing apparatus 1according to this embodiment will be described. As described above, theuser only designates the source coordinates and the destinationcoordinates in the color space. According to this designation, thecorrection range calculation unit 110 automatically calculates thecorrection range E, and the lattice point transfer distance calculationunit 120 calculates the destination coordinates of each lattice pointwithin the correction range E, and reflects the destination coordinateson the transformation rule (three-dimensional lookup table in thisembodiment). That is, even if the user does not have the knowledge andknow-how related to the color transformation (correction) processing inthe color space, the user can easily realize the color transformationprocessing (realize the memory color correction in the above-mentionedexample).

Further, the user has no need to sequentially set the transformationrule. That is, the user has no need to sequentially set the respectivetable data in the lookup table to be subjected to the memory colorcorrection. The user sets only the source coordinates and thedestination coordinates. As a result, the man-hour for setting by theuser can be reduced.

Further, the correction range calculation unit 110 according to thisembodiment rotates the correction range E according to the positionalrelationship between the source coordinates and the destinationcoordinates (rotates on an RG-axis plane, rotates on a GB-axis plane)(FIG. 5). In more detail, the correction range calculation unit 110rotates the correction range E so that a line connecting the sourcecoordinates and the destination coordinates becomes a long-axisdirection. With this operation, the memory color correction having nocolor space distortion can be conducted. The details will be describedwith reference to FIGS. 10A and 10B.

FIG. 10A is a diagram illustrating a change in the coordinates in thecolor space when the correction range is not rotated. As illustrated inFIG. 10A, the transfer distance of each coordinates positioned in thevicinity of the destination coordinates is rapidly changed.

FIG. 10B is a diagram illustrating a change in the coordinates in thecolor space when the correction range is rotated (that is, theconfiguration of the image processing apparatus 1 according to thisembodiment). As illustrated in FIG. 10B, the transfer distance of thelattice point coordinates (the magnitude of a transfer vector) is moregently changed as the source coordinates and the lattice pointcoordinates are farther from each other (for example, the amount ofcorrection indicated by (2) in FIG. 10B is larger than the amount ofcorrection indicated by (1) in FIG. 10A). This is because control ismade so that the transfer distance of each coordinates within thecorrection range is gradually smaller as the distance to the sourcecoordinates is larger. Because the color is not rapidly changed, thecolor space distortion can be avoided.

Further, according to image processing apparatus 1 of this embodiment,only the color to be corrected can be corrected. The advantages will bedescribed with reference to FIGS. 11A and 11B.

FIGS. 11A and 11B are conceptual diagrams illustrating the memory colorcorrection of a flesh color. FIG. 11A is a diagram illustrating thecorrection range E when the correction range E is not rotated. When thecorrection range E is not rotated, the coordinates indicative of colorsother than the color (flesh color) to be corrected are also to beunavoidably corrected. For that reason, the color not intended to becorrected by the user is unavoidably corrected (coordinates transfer inthe color space).

On the other hand, FIG. 11B is a diagram illustrating the correctionrange E when the correction range E is rotated (that is, theconfiguration of the image processing apparatus 1 according to thisembodiment). When the correction range E is rotated, only thecoordinates representative of the color (flesh color) to be correctedare to be corrected. Further, the destination coordinates of eachlattice point also fall within a range in which the flesh color exists.For that reason, the image processing apparatus 1 according to thisembodiment can appropriately correct only the color to be correctedwithout correcting the colors not intended to be corrected.

As has been described with reference to FIGS. 10A, 10B, 11A, and 11B,the image processing apparatus 1 according to this embodiment has suchan advantage that the correction quality is improved, in addition to theadvantages that the correction processing is realized without know-how,and the man-hour is reduced. When the user manually conducts thesetting, because the user focuses on the optimization of each settingitem, the occurrence of final color space distortion may be induced. Onthe other hand, the image processing apparatus according to thisembodiment determines the correction range E according to therelationship between the source coordinates and the destinationcoordinates. The transfer distance of the coordinates within thecorrection range E is controlled to be smaller as the distance to thesource coordinates is larger. For that reason, the image processingapparatus can generate an appropriate image without any color spacedistortion as described above.

The lattice point transfer distance calculation unit 120 within theimage processing apparatus 1 according to this embodiment includes thetransfer characteristic setting unit 126. However, the present inventionis not always limited to this configuration, but may calculate thetransformation destination coordinates directly from the degree ofinfluence Ef.

Second Embodiment

The image processing apparatus according to this embodiment ischaracterized in that the memory color correction taking a picture ofeach image (for example, each frame for moving pictures) into accountcan be realized. The image processing apparatus according to thisembodiment will be described below.

FIG. 12 is a block diagram illustrating a configuration of the imageprocessing apparatus according to this embodiment. The image processingapparatus 1 includes a picture adaptation unit 300 in addition to thetable data generation unit 100 and the three-dimensional lookup tableunit 200. The configurations and processing of the table data generationunit 100 and the three-dimensional lookup table unit 200 are identicalwith those in the first embodiment, and therefore the configuration andoperation of the picture adaptation unit 300 will be described below.

The picture adaptation unit 300 includes a storage color correctiontarget detection unit 301, a storage color correction determination unit302, a three-dimensional histogram generation unit 303, a histogramanalysis unit 304, and a source and destination calculation unit 305.

The storage color correction target detection unit 301 detects an objectand a background to be subjected to the memory color correction withinthe image (in the following description, the object and the backgroundare also collectively called “memory color correction target”). Thememory color correction target includes, for example, a face, sky, asea, red leaves, cherry blossoms, green of trees. The storage colorcorrection target detection unit 301 detects and analyzes the shapes,colors, brightness, and positions within an image (for example, upperportion of a screen: sky, lower portion of the screen: sea), of thosememory color correction targets. An image recognition techniquegenerally used may be used for the detection processing. In recentyears, the image recognition technique for detecting a specific memorycolor correction target has been developed widely in various fields. Inparticular, a large number of commercial products such as digital stillcameras have a function of face detection or the like.

The storage color correction target detection unit 301 supplies thedetected information (existence, shape, color, brightness, and positionwithin the image, of the memory color correction target) to the storagecolor correction determination unit 302 and the three-dimensionalhistogram generation unit 303 with the use of the general detectiontechnique for the memory color correction target.

The storage color correction determination unit 302 is a processing unitfor determining whether the memory color correction is conducted, ornot. The storage color correction determination unit 302 receivesinformation on the memory color correction target intended to becorrected by the user. In this embodiment, the user designates thememory color correction target to be corrected. In this example, theuser may designate a plurality of memory color correction targets. Whendesignating the plurality of memory color correction targets, the usersets a preset value of the source coordinates and a preset value of thedestination coordinates for each of the memory color correction targets.For example, when the memory color correction of blue sky and cherryblossoms is conducted at the same time, the user sets a preset value ofthe source coordinates and a preset value of the destination coordinatesrelated to the blue sky, and a preset value of the source coordinatesand a preset value of the destination coordinates related to the cherryblossoms.

The storage color correction determination unit 302 compares information(existence within the image, shape, color, brightness, and positionwithin the image, of the memory color correction target) with the memorycolor correction target designated by the user to determine whether thememory color correction is conducted, or not.

If no memory color correction target designated by the user existswithin the image, there is a possibility that no correct effect occurseven if the memory color correction is conducted. Further, there is arisk that an unintended memory color correction target may be subjectedto the memory color correction. For those reasons, the storage colorcorrection determination unit 302 determines whether the memory colorcorrection is conducted, or not.

The storage color correction determination unit 302 conductsdetermination for each of the images (frames). However, in a system (tobe described later) that holds a plurality of three-dimensional lookuptables or a system that can designate a correction area to be correctedby the three-dimensional lookup table, the storage color correctiondetermination unit 302 may conduct the above-mentioned determination(determination of whether to conduct the memory color correction) foreach of the areas in the screen. As a result, the memory colorcorrection further excellent in the precision can be realized.

The storage color correction determination unit 302 supplies thedetermination results to the source and destination calculation unit305.

The three-dimensional histogram generation unit 303 receives an RGBvalue of the entire input image as well as the information detected bythe storage color correction target detection unit 301. Thethree-dimensional histogram generation unit 303 generatesthree-dimensional histograms of the entire screen and an image area inwhich the memory color correction target is detected. Thethree-dimensional histogram generation unit 303 supplies two kinds ofgenerated three-dimensional histograms to the histogram analysis unit304.

The histogram analysis unit 304 analyzes the two kinds of inputthree-dimensional histograms (the three-dimensional histogram of theimage area in which the memory color correction target is detected, andthe three-dimensional histograms of the entire image). First, adescription will be given of the analysis of the three-dimensionalhistograms of the image area in which the memory color correction targetis detected.

The same object or the same background is displayed in the image area inwhich the memory color correction target is detected. For example,pixels configuring the blue sky exist in an area where the blue sky isdetected. For that reason, it is assumed that, in the histogram in thecolor space, values are concentrated on a given area within thethree-dimensional space. In this example, in the histogram, colorcoordinates having a given frequency or lower are ignored. As a result,the histogram having an oval spherical shape centered on the colorcoordinates within the three-dimensional space can be obtained. Thehistogram analysis unit 304 detects coordinates of the center of theoval spherical shape, that is, coordinates of the main color of thememory color correction target as the analysis results. In the detectionmethod, two kinds of oval sphere position center detection and ovalsphere gravity center detection are mainly conceivable. First, the ovalsphere position center detection will be described.

The histogram analysis unit 304 defines the maximum values, the minimumvalues, and center values of the respective axes of RGB within the ovalsphere related to the above-mentioned histogram as follows, andcalculates a center value of the oval sphere through the followingexpression.

Maximum values within the oval sphere: Rmax, Gmax, Bmax

Minimum values within the oval sphere: Rmin, Gmin, Bmin

Center values within the oval sphere: Rcen, Gcen, Bcen

$\begin{matrix}{{{Rcen} = \frac{( {{Rmax} - {Rmin}} )}{2}},{{Gcen} = \frac{( {{Gmax} - {Gmin}} )}{2}},{{Bcen} = \frac{( {{Bmax} - {Bmin}} )}{2}}} & ( {{Ex}.\mspace{14mu} 32} )\end{matrix}$

Subsequently, the oval sphere gravity center detection will bedescribed. The histogram analysis unit 304 defines accumulated valuesand oval sphere gravity center values of the respective axes of RGBwithin the above-mentioned oval sphere as follows, and calculates agravity center value of the oval sphere through the following Expression33.

Accumulated values within the oval sphere: Rsgm, Gsgm, Bsgm

The total number of pixels: Dot

Gravity center values within the oval sphere: Rgra, Ggra, Bgra

$\begin{matrix}{{{{Rsgm} = {\sum\limits_{n = 1}^{Dot}\;{Rn}}},{{Gsgm} = {\sum\limits_{n = 1}^{Dot}\;{Gn}}},{{Bsgm} = {\sum\limits_{n = 1}^{Dot}\;{Bn}}}}{{{Rgra} = \frac{Rsgm}{Dot}},{{Ggra} = \frac{Gsgm}{Dot}},{{Bgra} = \frac{Bsgm}{Dot}}}} & ( {{Ex}.\mspace{14mu} 33} )\end{matrix}$

The histogram analysis unit 304 may calculate the center/gravity center(that is, the coordinates of the main color of the object or background)of the oval sphere within the histogram through a method other than theabove method. The histogram analysis unit 304 supplies the coordinatesobtained by analysis to the source and destination calculation unit 305.

Subsequently, a description will be given of the analysis of thehistogram of the entire image by the histogram analysis unit 304. Thehistogram analysis unit 304 analyzes how the histogram is shaped betweenthe preset value of the source coordinates and the preset value of thedestination coordinates which are set for each of the memory colorcorrection targets by the user, and in the color coordinates of theperiphery. In more detail, the histogram analysis unit 304 analyzeswhether color has already existed in the vicinity of the preset value ofthe destination coordinates in a state before the memory colorcorrection (whether a plurality of coordinates having the color similarto the color of the destination has exited). Also, the histogramanalysis unit 304 analyzes a distribution rate of the colors between thepreset value of the source coordinates and the preset value of thedestination coordinates.

A description will be given in detail of the analysis of the histogramof the entire image by the histogram analysis unit 304 with reference toFIG. 13. In FIG. 13, seven areas are set between a preset value OP ofthe source coordinates and a preset value TP of the destinationcoordinates. In FIG. 13, for convenience of description, two-dimensionalcoordinate space is illustrated. However, the histogram analysis unit304 really deals with the three-dimensional coordinate space.

The histogram analysis unit 304 analyzes the histogram for each of theseven areas. The histogram analysis unit 304 determines whether thenumber of pixels located in each of the areas exceeds a given thresholdvalue, or not. If exceeding, the histogram analysis unit 304 determinesthat color exists in the above area before correction (a given number ofpixels or more exist in the above area before correction). Thedetermination is conducted in the order from an area 1 closer to thepreset value of the source coordinates to an area 7. The histogramanalysis unit 304 completes the determination processing when detectingthe area in which the given number of pixels or more can be confirmed.The histogram analysis unit 304 detects representative coordinates ofthe area in which the given number of pixels or more can be confirmed asexisting coordinates TE(TEr, TEg, TEb). The histogram analysis unit 304supplies the existing coordinates TE(TEr, TEg, TEb) to the source anddestination calculation unit 305.

For example, if the given number of pixels or more do not exist in thearea 1, and the given number of pixels or more exist in the area 2, thehistogram analysis unit 304 does not conduct the determination relatedto the area 3 and subsequent areas. Then, the histogram analysis unit304 detects the representative coordinates of the area 2 as the existingcoordinates TE(TEr, TEg, TEb). The determination to the area 7 isdetermined, and if there is no area in which the given number of pixelsor more exist, the histogram analysis unit 304 considers that thereexists no existing coordinates TE.

In the description of FIG. 13, seven areas are provided in thehistogram, but the present invention is not always limited to thisconfiguration. If the number of areas is increased more, the histogramanalysis unit 304 can detect the existing coordinates in detail. Thatis, a precision in the existence determination can be improved. As aresult, the setting precision in the destination coordinates of thememory color correction which will be described later can be improved.

Subsequently, the source and destination calculation unit 305 will bedescribed. In this embodiment, the user sets the preset value OP of thesource coordinates O and the preset value TP of the destinationcoordinates T for each object or background to be corrected. The sourceand destination calculation unit 305 calculates the source coordinates Oand the destination coordinates T to be supplied to the table datageneration unit 100 on the basis of the preset values, the determinationresults of the storage color correction determination unit 302, and theanalysis results of the histogram analysis unit 304. That is, in thisembodiment, the source coordinates and the destination coordinates whichare input by the user are not used as they are, but the coordinateposition is adjusted and supplied to the table data generation unit 100.

First, a description will be given of calculation processing of thesource coordinates O by the source and destination calculation unit 305.The user sets the preset value OP(OPr, OPg, ORb) of the sourcecoordinates for each of the memory color correction targets. The sourceand destination calculation unit 305 receives the analysis results ofthe histogram analysis unit 304. The analysis results are center colorcoordinates OC(OCr, OCg, OCb) of the memory color correction targetdesignated by the user. The source and destination calculation unit 305calculates the source coordinates O(Ro, Go, Bo) between the preset valueOP(OPr, OPg, ORb) and the center color coordinates OC(OCr, OCg, OCb)through Expression 34 which will be described later. The user can set afollowing degree F1 (0 to 100%) which is an index of how much the presetvalue of the source coordinates can approach the center colorcoordinates OC(OCr, OCg, OCb). If the following degree F1 is set to 0%,the source coordinates O are equal to the preset value OP(OPr, OPg, ORb)of the source coordinates O. If the following degree F1 is set to 100%,the source coordinates O are equal to the center color coordinatesOC(OCr, OCg, OCb). If the following degree F1 is set to 50%, the sourcecoordinates O are an intermediate value between the preset value OP(OPr,OPg, ORb) of the source coordinates O and the center color coordinatesOC(OCr, OCg, OCb). A formula for computation (Ex. 34) of the sourcecoordinates O(Ro, Go, Bo) is represented as follows.Ro=OPr+(OCr−OPr)×F1Go=OPg+(OCg−OPg)×F1Bo=OPb+(OCb−OPb)×F1  (Ex. 34)

It is assumed that the following degree F1 is set to about 50%, and adefault value when the user does not designate the following degree F1is also set to about 50%.

Subsequently, a description will be given of the calculation processingof the destination coordinates by the source and destination calculationunit 305. The user sets the preset value TP(TPr, TPg, TRb) of the sourcecoordinates for each of the memory color correction targets. The sourceand destination calculation unit 305 receives the analysis results ofthe histogram analysis unit 304, and determines whether a given numberof pixels or more have already existed in a direction the destination ina state before correction, or not. If existing, the source anddestination calculation unit 305 calculates final destinationcoordinates T on the basis of the input existing coordinates TE(TEr,TEg, TEb) and the preset value TP(TPr, TPg, TRb) of the destinationcoordinates T through Expression 35 that will be described later. Theuser can set a following degree F2 (0 to 100%) which is an index of howmuch the preset value of the destination coordinates T can approach theexisting coordinates TE. If the following degree F2 is set to 0%, thedestination coordinates T are equal to the preset value TP(TPr, TPg,TRb) of the destination coordinates T. If the following degree F2 is setto 100%, the destination coordinates T are equal to the existingcoordinates TE(TEr, TEg, TEb). If the following degree F2 is set to 50%,the destination coordinates T are an intermediate value between thepreset value TP(TPr, TPg, TRb) of the destination coordinates T and theexisting coordinates TE(TEr, TEg, TEb). A formula for computation (Ex.35) of the destination coordinates T(Rt, Gt, Et) is represented asfollows.Rt=TPr+(TEr−TPr)×F2Gt=TPg+(TEg−TEg)×F2Rt=TPr+(TEb−TPb)×F2  (Ex. 35)

It is assumed that the following degree F2 is set to about 50%, and adefault value when the user does not designate the following degree F2is also set to about 50%.

The source and destination calculation unit 305 supplies the calculatedsource coordinates O(Ro, Go, Bo) and the destination coordinates T(Rt,Gt, Bt) to the table data generation unit 100.

Subsequently, a description will be given of problems on the memorycolor correction not taking the picture into account, and the advantagesof the image processing apparatus 1 according to this embodiment. First,the problems on the memory color correction not taking the picture intoaccount will be described.

In the memory color correction not taking the picture into account, thecorrection processing is conducted with the aid of the lookup table towhich one steady pattern has been input regardless of the presence orabsence of the memory color correction target. For that reason, there isa risk that the pixels of the unintentional memory color correctiontarget unintended to be corrected are unavoidably corrected.

Further, even if the memory color correction target intended to becorrected by the user exists within the image, because the memory colorcorrection target (for example, a person's face) has a color differentfrom a color area assumed as the memory color correction target, thereis a risk that the pixels to be corrected cannot be sufficientlyincluded within the correction range.

In the memory color correction using the lookup table, the correction isfrequently conducted on a plurality of memory color correction targetsat the same time. In this case, the correction ranges may interfere witheach other. The status will be described with reference to FIG. 14. Asillustrated in FIG. 14, the correction range related to one memory colorcorrection target may interfere with the correction range related toanother memory color correction target. In this case, it is unclear howthe correction is conducted within the interfering areas. For thatreason, there is a need to conduct processing while suppressing acorrection intensity more than a generally ideal amount of correction.That is, the correction processing is conducted after the correctionrange is reduced as illustrated in FIG. 14. For that reason, asufficient correction effect can be obtained.

Subsequently, a description will be given of the advantages of the imageprocessing apparatus 1 according to this embodiment. The imageprocessing apparatus 1 according to this embodiment detects the memorycolor correction target, and automatically calculates the sourcecoordinates and the destination coordinates on the basis of thehistograms of the memory color correction target and the entire image.As a result, the image processing apparatus 1 according to the firstembodiment can obtain the following two advantages.

(1) The correction processing can be conducted on only the memory colorcorrection target intended to be corrected by the user.

(2) The correction with a sufficient intensity can be conducted on thememory color correction target intended to be corrected by the user.

First, a description will be given of a reason why there can be obtainedthe advantage that “the correction processing can be conducted on onlythe memory color correction target intended to be corrected by the user”in the image processing apparatus 1 according to this embodiment.

The storage color correction determination unit 302 calculates whetherthere is the memory color correction target designated by the user, ornot. Only when there is the memory color correction target designated bythe user, the source and destination calculation unit 305 calculates thesource coordinates and the destination coordinates T. As a result, theimage processing apparatus 1 (three-dimensional lookup table unit 200)can conduct only the memory color correction related to the memory colorcorrection target, that is, obtain the above-mentioned advantage (1).

If a plurality of memory color correction targets do not exist withinone screen, that is, if only one memory color correction target exists,the image processing apparatus 1 conducts the memory color correction onthe single memory color correction target. For that reason, the imageprocessing apparatus 1 has no need to cope with the interference of thecorrection ranges.

The storage color correction determination unit 302 determines thatthere are the plurality of memory color correction targets designated bythe user, and if both of the correction ranges interfere with eachother, the image processing apparatus 1 could conduct unintendedtransformation on the color coordinates belonging to the interferencearea. However, this problem is solved by a configuration of a fourth orfifth embodiment which will be described later.

Subsequently, a description will be given of reasons why there can beobtained the advantage that “(2) The correction with a sufficientintensity can be conducted on the memory color correction targetintended to be corrected by the user.” in the image processing apparatus1 according to this embodiment. The following two reasons will bedescribed.

A first reason will be described below. As described above, the storagecolor correction determination unit 302 calculates whether there is thememory color correction target designated by the user, or not. Then, thesource and destination calculation unit 305 sets the correction rangefor only the memory color correction target designated by the user anddetected. That is, for example, in FIG. 14, the correction range can belimited to only the memory color correction target designated by theuser. For that reason, the number of oval spheres indicative of thecorrection ranges in the color space can be reduced. As a result, a needto taking the interference of the correction ranges of the memory colorcorrection into account is reduced, and a need to take action such as areduction in the correction range can be reduced. Because a need toreduce the correction range is reduced, the correction with a sufficientintensity can be conducted.

Subsequently, a second reason why the above-mentioned advantage (2) isobtained will be described with reference to FIGS. 15A and 15B. In thedescription of FIGS. 15A and 15B, it is assumed that there are an areaindicative of blue sky and an area indicative of a blue flower in animage to be processed. It is assumed that the user intends to conductonly the memory color correction of blue sky.

FIG. 15A is a conceptual diagram illustrating the memory colorcorrection by the image processing apparatus 1 according to the firstembodiment. In this case, the image processing apparatus 1 determinesthe correction range with the use of the source coordinates and thedestination coordinates, which are input by the user, as they are. Forthat reason, if the objects having similar colors such as the blue skyand the blue flower exist within the image, the image processingapparatus 1 unintentionally changes the color of the blue flowerunintended to be corrected.

FIG. 15B is a conceptual diagram illustrating the memory colorcorrection by the image processing apparatus 1 according to thisembodiment. The histogram analysis unit 304 determines whether a givennumber of pixels or more exist between the preset value of the sourcecoordinates and the preset value of the destination coordinates, or not.If the given number of pixels or more do not exist, the source anddestination calculation unit 305 sets the preset value of the sourcecoordinates as the source coordinates as it is, and sets the presetvalue of the destination coordinates as the destination coordinates asit is. As a result, the image processing apparatus 1 can conduct thememory color correction with the sufficient intensity.

On the other hand, if the given number of pixels or more exist, thesource and destination calculation unit 305 transfers the preset value(coordinates) of the destination coordinates in a direction closer tothe preset value of the source coordinates, and determines the transferpoint as the destination coordinates. For example, if the blue sky andthe blue flower are displayed within the image, the image processingapparatus 1 moves the preset value of the destination coordinates closerto the preset value of the source coordinates, and conducts the memorycolor correction (refer to FIG. 15B). In this example, the source anddestination calculation unit 305 appropriately adjusts the transferdistance of the preset value (coordinates) according to an area in whichthe given number of pixels or more exists. As a result, as illustratedin FIG. 15B, the image processing apparatus 1 can conduct the memorycolor correction of the object (background) to be corrected whileautomatically calculating a range in which the object (background) notto be corrected is not affected.

As described above, the general image processing apparatus reduces thecorrection range of the memory color correction without any exceptiontaking adverse effects on the other objects (background) into account.However, the image processing apparatus 1 according to this embodimentanalyzes an existence position of the color within the color space(conducts the above-mentioned histogram analysis) to detect apossibility that another object not intended to be corrected exists withthe result that an optimum correction range can be determined for eachof the frames (images). With the above configuration, the imageprocessing apparatus 1 according to this embodiment can realize thememory color correction having the sufficient amount of correctionaccording to the picture of the image (frame).

In a moving image, the picture is changed with time. The imageprocessing apparatus 1 according to this embodiment appropriatelyadjusts the source coordinates and the destination coordinates used forthe memory color correction in compliance with a change in the picture.For that reason, the image processing apparatus 1 according to thisembodiment can realize the memory color correction with high precisionwith respect to the moving image.

In the above description, the picture adaptation unit 300 adjusts thepreset value of the source coordinates and the preset value of thedestination coordinates. However, the present invention is not alwayslimited to this configuration, but the picture adaptation unit 300 mayadjust any one of those preset values. For example, the pictureadaptation unit 300 adjusts only the preset value of the sourcecoordinates, and applies the destination coordinates input by the useras they are. Even with the above configuration, the image processingapparatus 1 can obtain specific advantages.

Third Embodiment

An image processing apparatus according to this embodiment ischaracterized in that the number of table data items held in thethree-dimensional lookup table can be limited. It is assumed that theimage processing apparatus according to this embodiment mainly conductsdynamic processing on the moving image (processing for analyzing thepicture and conducting the memory color correction according to thepicture). The image processing apparatus according to this embodiment isa modification of the second embodiment, and therefore differences(configuration and operation of the correction range calculation unit110) from the second embodiment will be mainly described.

FIG. 16 is a block diagram illustrating a configuration of thecorrection range calculation unit 110 according to this embodiment. Thecorrection range calculation unit 110 includes a transformed coordinatenumber limit unit 116 in addition to the configuration of FIG. 3.

The user sets a table data limit number set for the three-dimensionallookup table to the transformed coordinate number limit unit 116. Inthis example, the table data limit number means an upper limit number ofthe lattice points set as transformation targets for thethree-dimensional lookup table. For example, the user may set the tabledata limit number taking into account the type of moving image data tobe subjected to the memory color correction, the image data size (thenumber of pixels in a matrix) of the moving image data, and a requiredoperation speed.

The transformed coordinate number limit unit 116 receives an oval sphereexpression of each memory color correction target which is calculated bythe correction range oval sphere expression calculation unit 115. Forexample, when the memory color correction of the blue sky and the memorycolor correction of the cherry blossoms are conducted, two oval sphereexpressions are input to the transformed coordinate number limit unit116. The transformed coordinate number limit unit 116 calculates a totalnumber of lattice points to be corrected on the basis of those ovalsphere expressions. The number of lattice points included within theoval spheres can be calculated from those oval sphere expressions on thebasis of the lattice point distances (FIG. 17A). In this example, thetransformed coordinate number limit unit 116 calculates the total numberof lattice points to be corrected on the basis of all of the oval sphereexpressions to be corrected. The transformed coordinate number limitunit 116 compares the table data limit number input from the user withthe total number of lattice points to be corrected which are calculatedon the basis of the oval sphere expressions.

If the table data limit number is equal to or larger than the totalnumber of lattice points to be corrected, the transformed coordinatenumber limit unit 116 instructs the correction range oval sphereexpression calculation unit 115 on an output of the oval sphereexpressions.

On the other hand, if the table data limit number is smaller than thetotal number of lattice points to be corrected, the transformedcoordinate number limit unit 116 instructs the correction range gain andoffset adjustment unit 112 to readjust a gain and/or an offset. In thisexample, the transformed coordinate number limit unit 116 notifies thecorrection range gain and offset adjustment unit 112 of a ratio of thetable data limit number to the total number of lattice points to becorrected. Then, the transformed coordinate number limit unit 116instructs the correction range oval sphere expression calculation unit115 to prohibit the output of the oval sphere expressions.

The correction range gain and offset adjustment unit 112 resets the gainand/or the offset so as to decrease the oval spheres with reference tothe notified ratio (FIG. 17B). Because of resetting the gain and/or theoffset with reference to the ratio, the correction range gain and offsetadjustment unit 112 can avoid the oval sphere from being more downsizedthan necessary.

After resetting the gain and/or the offset, the correction range ovalsphere expression calculation unit 115 again calculates the oval sphereexpression.

In the above-mentioned description, the correction range is reduced byadjusting the gain and/or the offset. However, the present invention isnot always limited to this configuration. For example, the sourcecoordinates and/or the destination coordinates to be subjected to thememory color correction may transfer to reduce the correction range. Forexample, in the example of FIG. 17B, the destination coordinates isallowed to transfer to a position indicated by a dotted line to reducethe correction range of the memory color correction target. This isachieved by allowing the transformed coordinate number limit unit 116 toinstruct the picture adaptation unit 300 to change the positions of thesource coordinates and/or the destination coordinates to be subjected tothe memory color correction.

Subsequently, a description will be given of the advantages of the imageprocessing apparatus according to this embodiment. A general problem onthe dynamic processing using the three-dimensional lookup table residesin that a large number of table data is set. Because the number of tabledata items is large, it is difficult to use the three-dimensional lookuptable in processing of the moving image data where data is sequentiallyinput.

The image processing apparatus according to this embodiment limits thenumber of table data items to be equal to or smaller than the table datalimit number input by the user. That is, the image processing apparatus1 according to this embodiment limits the number of table data itemsstored in the lookup table of the table size such as 729 (9×9×9) or 4913(17×17×17) to the table data limit number or lower. For example, theimage processing apparatus 1 limits the number of table data itemsstored in the lookup table having a capacity of 729 (9×9×9) to 200. As aresult, the number of data items to be transferred within a unit timecan be prevented from being increased, and the high processing speed ofthe entire system can be realized.

In the above-mentioned description, the number of data items stored inthe three-dimensional lookup table is reduced by downsizing the ovalsphere. However, the present invention is not always limited to thisconfiguration. For example, the correction range oval sphere expressioncalculation unit 115 may reduce the number of memory color correctiontargets to be processed to reduce the number of data items.

Fourth Embodiment

An image processing apparatus according to this embodiment conducts thememory color correction taking the priority order into account if thereare a plurality of memory color correction targets. As described above,in the memory color correction using one three-dimensional lookup table,the color areas may interfere with each other. As a result, the memorycolor correction to the plurality of targets cannot be executed at thesame time. Also, sufficient correction may not be conducted. In thisembodiment, the user sets the priority order of the memory colorcorrection for each of the objects or the background for the imageprocessing apparatus. The image processing apparatus according to thisembodiment conducts an optimum memory color correction according to thepriority order even if the plurality of objects are subjected to thememory color correction. Hereinafter, the configuration of the imageprocessing apparatus according to this embodiment will be described withreference to FIG. 18. Further, an operation image according to thisembodiment will be described appropriately with reference to FIG. 19.

The correction range calculation unit 110 includes a correction rangeoverlap detection unit 117 in addition to the configuration of FIG. 3.The priority order (the priority order is higher as numerical values aresmaller) of the memory color correction targets is supplied to thecorrection range overlap detection unit 117. The user sets the priorityorder. For example, the user enters “priority order 1: blue sky”,“priority order 2: blue flower”, and “priority order 3: cherryblossoms”.

The oval sphere expressions of the respective memory color correctiontargets, which are calculated by the correction range oval sphereexpression calculation unit 115, are input to the correction rangeoverlap detection unit 117. The correction range overlap detection unit117 determines whether there is an overlap portion in the oval sphere,or not, if there are a plurality of oval sphere expressions. Forexample, in an example of FIG. 19, the overlap portion exists between anoval sphere of the memory color correction related to the object of thepriority order 1, and an oval sphere of the memory color correctionrelated to the object of the priority order 2. The correction rangeoverlap detection unit 117 can determine whether there is the overlapportion, or not, through known processing in the three-dimensional spacefrom the given oval sphere expression.

If there is the overlap portion, the correction range overlap detectionunit 117 notifies the correction range gain and offset adjustment unit112 of the memory color correction target lower in the priority orderand a size of an overlap range. Then, the correction range overlapdetection unit 117 instructs the correction range oval sphere expressioncalculation unit 115 to prohibit the output of the oval sphereexpression.

If there is no overlap portion, the correction range overlap detectionunit 117 instructs the correction range oval sphere expressioncalculation unit 115 to output the oval sphere expression.

Upon receiving a notice from the correction range overlap detection unit117, the correction range gain and offset adjustment unit 112 adjuststhe gain or/and the offset so that the oval sphere of the memory colorcorrection target lower in the priority order becomes smaller. In thisexample, the correction range gain and offset adjustment unit 112adjusts the gain or/and the offset according to the size of the overlaprange. Then, the correction range gain and offset adjustment unit 112supplies the correction range calculated after adjustment for each ofRGB to the correction range oval sphere expression calculation unit 115.

In the example of FIG. 19, the correction range gain and offsetadjustment unit 112 changes the correction range of the priority order 2(correction range lower in the priority order) to a correction rangeindicated by a dotted line by adjustment of the gain and/or the offset,and supplies the changed correction range to the correction range ovalsphere expression calculation unit 115.

If there is the overlap portion, the memory color correction may not beconducted on the memory color correction target lower in the priorityorder.

Subsequently, the advantages of the image processing apparatus accordingto this embodiment will be described. First, a problem on the memorycolor correction not taking the priority order into account will bedescribed. As illustrated in FIG. 19, if a plurality of memory colorcorrection targets are dealt with, the correction ranges may overlapwith each other. In this case, there is a need to take action for givingup correction of one memory color correction target, or the like. Forthat reason, the intended memory color correction effect may not beobtained.

On the other hand, the image processing apparatus according to thisembodiment can set the priority order of the memory color correctiontargets if there are a plurality of memory color correction targets.Then, the image processing apparatus according to this embodiment cansecure that the memory color correction with a desired intensity issurely conducted on the memory color correction target higher in thepriority order. Further, if the correction ranges do not overlap witheach other, the image processing apparatus according to this embodimentcan conduct the memory color correction with the sufficient correctionintensity even on the memory color correction target lower in thepriority order.

Further, if the correction ranges overlap with each other, thecorrection range gain and offset adjustment unit 112 adjusts the gainand/or the offset to the degree that eliminates the overlap. For thatreason, even if the correction ranges overlap with each other, the imageprocessing apparatus according to this embodiment can conduct a givenmemory color correction on the memory color correction target lower inthe priority order.

That is, according to the image processing apparatus of this embodiment,the memory color correction can be executed on a plurality of memorycolor correction targets belonging to the same (approximate) color areaaccording to the user's intention.

Further, the configuration according to the third embodiment and theconfiguration according to the fourth embodiment can be combinedtogether. That is, the image processing apparatus 1 may adjust thecorrection range to be narrowed according to the priority order so thatthe number of table data items becomes equal to or smaller than thetable data limit number. In this case, even if the correction ranges donot overlap with each other, the correction ranges are reduced. Thisconcept will be described below.

First, the correction range calculation unit 110 calculates thecorrection ranges (oval sphere expressions) of the respective memorycolor correction targets without taking the table data limit number intoaccount. In this case, it is assumed that the number of table data itemsto be set for each of the frames exceeds the table data limit number(exceeds the capability of the system). However, if the user determinesthe priority order of the respective memory color correction targets inadvance, the image processing apparatus 1 adjusts the respectivecorrection ranges in such a manner that the reduction ratio of thecorrection range becomes higher as the priority order is lower so thatthe number of table data items becomes equal to or smaller than thetable data limit number.

The operation concept will be described with reference to FIGS. 20A and20B. In an example of FIGS. 20A and 20B, three memory color correctiontargets are set. In FIG. 20A, the memory color correction target of thepriority order 1 does not exist within the frame. For that reason, thecorrection range calculation unit 110 adjusts the correction rangeswithout remarkably reducing the correction range of the memory colorcorrection target of the priority order 2 and the correction range ofthe memory color correction target of the priority order 3.

On the other hand, in FIG. 20B, the memory color correction target ofthe priority order 1 exists within the frame. For that reason, thecorrection range calculation unit 110 remarkably reduces the correctionrange of the memory color correction target of the priority order 2 andthe correction range of the memory color correction target of thepriority order 3. On the other hand, the correction range calculationunit 110 minimizes a reduction in the correction range of the memorycolor correction target of the priority order 1.

A specific numerical value of the reduction ratio corresponding to thepriority order can be appropriately designated by the user.

Thus, taking both of the priority order and the table data limit numberinto account, the image processing apparatus 1 can sufficiently ensurethe correction intensity of the memory color correction target to besubjected to the memory color correction while suppressing the tabledata to a desired number.

Fifth Embodiment

An image processing apparatus according to this embodiment ischaracterized in that a plurality of three-dimensional lookup tables canbe held. The image processing apparatus according to this embodiment isa modification of the image processing apparatus according to the secondembodiment, and therefore differences from the image processingapparatus according to the second embodiment will be mainly described.

FIG. 21 is a block diagram illustrating a configuration of the imageprocessing apparatus 1 according to this embodiment. The imageprocessing apparatus 1 includes a plurality of three-dimensional lookuptable units 200 to 202, and a selector 400 in addition to theconfiguration of FIG. 1.

The storage color correction target detection unit 301 detects thememory color correction target, and also detects in which area each ofthe memory color correction targets exists within the image, that is,the display area of each memory color correction target within theimage. The processing of the storage color correction target detectionunit 301 will be described with reference to FIG. 22.

In the following example, the storage color correction target detectionunit 301 detects three of “blue sky”, “blue flower”, and “person's skin”as the memory color correction targets. Also, the user sets “blue sky”and “blue flower” as the memory color correction targets. FIG. 22 is adiagram illustrating an example of an image to be corrected. Asillustrated in the figure, blue sky exists on an upper portion of theimage, and blue flowers exist on a lower left portion of the screen. Theuser sets source coordinates (RGB value) and destination coordinates(RGB value) in the color space for “blue sky” and “blue flowers”. Thestorage color correction target detection unit 301 notifies the selector400 which memory color correction target exists in each pixel within theimage. For example, the storage color correction target detection unit301 notifies the selector 400 that the blue sky exists on a pixel 1 (X1,Y1) of FIG. 22. Likewise, the storage color correction target detectionunit 301 notifies the selector 400 that the blue flowers exist on apixel 2 (X2, Y2) of FIG. 22. If the memory color correction target doesnot exist on a pixel to be processed, the storage color correctiontarget detection unit 301 notifies the selector 400 of this fact.

The correction range calculation unit 110 calculates the correctionranges of the respective memory color correction targets in the samemanner as that in the first embodiment. FIG. 23 is a diagramillustrating the correction range of the blue sky and the correctionrange of the blue flowers. In this example, there exists an overlaprange D1 of the correction range of the blue sky and the correctionrange of the blue flower.

The lattice point transfer distance calculation unit 120 calculates thetransfer distance of each lattice point for each of the input memorycolor correction targets. In an example of FIG. 23, the lattice pointtransfer distance calculation unit 120 calculates the destinationcoordinates of each lattice point included within the correction rangeof the blue sky, and also calculates the destination coordinates of eachlattice point included within the correction range of the blue flowers.For that reason, the lattice point transfer distance calculation unit120 calculates P2 as transformed coordinates when the coordinates P1 isdealt with as the lattice point included within the correction range ofthe blue sky. The lattice point transfer distance calculation unit 120calculates P3 as the transformed coordinates when the coordinates P1 isdealt with as the lattice point included within the correction range ofthe blue flowers.

The lattice point transfer distance calculation unit 120 calculates thetransformed coordinates of each lattice point for each of the memorycolor correction targets. Then, the lattice point transfer distancecalculation unit 120 sets the three-dimensional lookup table for each ofthe memory color correction targets. In the following example, thelattice point transfer distance calculation unit 120 sets the table datarelated to the memory color correction of the blue sky in thethree-dimensional lookup table unit 200, sets the table data related tothe memory color correction of the blue flower in the three-dimensionallookup table unit 201, and sets the table data for the other colorcorrection in the three-dimensional lookup table unit 202.

The respective lookup table units (200 to 202) correct the respectivepixels in the color space according to the set lookup tables. Therespective lookup table units (200 to 202) output the RGB values of therespective pixels obtained by correction to the selector 400.

As described above, the selector 400 is notified of the existencecoordinates of the respective memory color correction targets from thestorage color correction target detection unit 301. The selector 400selects and outputs one of the RGB values output from the lookup tableunits (200 to 202) according to a relationship between the pixelposition and the existence coordinates of the respective memory colorcorrection targets. For example, when the pixel 1 is corrected in FIG.22, the selector 400 selects and outputs the output from the lookuptable unit 200 (processing unit in which the table data of the memorycolor correction of the blue sky is set). Likewise, when the pixel 2 iscorrected in FIG. 22, the selector 400 selects and outputs the outputfrom the lookup table unit 201 (processing unit in which the table dataof the memory color correction of the blue flowers is set).

Subsequently, a description will be given of the advantages of the imageprocessing apparatus according to this embodiment. As described above,the image processing apparatus 1 according to this embodiment providesthe lookup table for each of the memory color correction targets. Theimage processing apparatus 1 selects an appropriate value from thetransformation results of the plurality of lookup tables according tothe existence positions of the respective memory color correctiontargets within the image. As a result, as illustrated in FIG. 23, evenif the correction ranges overlap with each other in the color space, theimage processing apparatus 1 can appropriately conduct the memory colorcorrection without being affected by the overlap of the correctionranges.

In the above description, the image processing apparatus 1 includes thelookup table for each of the memory color correction targets. However,the present invention is not limited to this configuration. The imageprocessing apparatus 1 may store the table data in another lookup tableonly when the correction ranges overlap with each other. For example, itis assumed that the correction range of the blue sky and the correctionrange of the blue flowers overlap with each other, but the correctionrange of the blue sky and the correction range of the cherry blossoms donot overlap with each other. In this case, the table data related to thecorrection range of the cherry blossoms is stored in a first lookuptable in addition to the table data related to the correction range ofthe blue sky. Then, the table data related to the correction range ofthe blue flowers is stored in a second lookup table. This makes itpossible to realize the memory color correction processing that is notaffected by the overlap of the correction ranges while minimizing anincrease in the number of lookup tables.

Sixth Embodiment

An image processing apparatus according to this embodiment ischaracterized in that an image signal other than the RGB can be dealtwith. In the image processing apparatus according to this embodiment,the user can set source coordinates of the memory color correctiontarget and a transfer distance from that coordinates. In the imageprocessing apparatus according to this embodiment, differences from thefirst embodiment will be mainly described.

The image processing apparatus 1 according to this embodiment ischaracterized in that a color space transformation unit 500 is providedupstream of the table data generation unit 100 (or the pictureadaptation unit 300). FIG. 24 is a block diagram illustrating aconfiguration of the color space transformation unit 500. The colorspace transformation unit 500 includes an RGB/HSV transformation unit510, an adder 520, and an HSV/RGB transformation unit 530.

The user designates source coordinates O(Ro, Go, Bo) and a variationfrom the source coordinates. In this example, the variation isdesignated in each item of, for example, hue (H), saturation (S), andbrightness (V).

The RGB/HSV transformation unit 510 transforms the source coordinatesdesignated by the user from an RGB values to an HSV value. Thistransformation may be conducted by a known technique. The RGB/HSVtransformation unit 510 outputs the transformed HSV value (Ho, So, Vo)to the adder 520.

The adder 520 adds the variation (ΔH, ΔS, ΔH) in the respective items ofhue (H), saturation (S), and brightness (V) to the input HSV value (Ho,So, Vo). The adder 520 outputs an added value (Ht, St, Vt) to theHSV/RGB transformation unit 530.

The HSV/RGB transformation unit 530 transforms the HSV value (Ht, St,Vt) which is the input added value to the RGB value. The RGB valuerepresents destination coordinates T(Rt, Gt, Bt). The HSV/RGBtransformation unit 530 supplies the destination coordinates T to thetable data generation unit 100. To the table data generation unit 100 isalso supplied source coordinates of the RGB format designated by theuser.

Through the above processing, the source coordinates O and thedestination coordinates T are set in the table data generation unit 100.The subsequent respective processing is identical with that in the firstembodiment.

Subsequently, a description will be given of the advantages of the imageprocessing apparatus 1 according to this embodiment. Even when thememory color correction is intended to be conducted, intended colorcoordinates may not be determined. In this embodiment, the user candesignate the variation from the source coordinates instead of thedestination coordinates. For that reason, the user conducts ambiguousdesignations such as “little yellow”, “darker color”, or “very bright”,and can convert the designation to the variation. As a result, a loadfor setting by the user is further reduced.

In the above-mentioned example, the transformation of the HSV and theRGB is conducted. However, the present invention is not always limitedto this configuration. For example, the user inputs the sourcecoordinates and the variation in the RGB format. Then, the adder maycalculate the destination coordinates through addition processing.

In the example of FIG. 24, the transformation of the HSV value and theRGB value is described. However, the present invention is not alwayslimited to this configuration, and transformation may be conductedbetween an HSU value, a YUV value, an HLS value, an Lab value, or an YCMvalue, and the RGB value.

The image processing apparatus according to the present invention hasbeen described above along the embodiments. However, the presentinvention is not limited to the above respective embodiments, and can beappropriately changed without departing from the subject matter of thepresent invention. In the above-mentioned embodiments, the coordinatetransformation processing is conducted assuming that the color space isthe RGB space. However, the present invention can be applied to othercolor spaces. That is, the image processing apparatus may conduct theabove-mentioned respective processing in the color spaces of the HSV,HSU, YUV, HLS, Lab, and YCM.

The above image processing apparatus 1 is incorporated into, forexample, a printer device, a TV receiver, a copying machine, a digitalmultifunction machine, a projector device, a cellular phone terminal, adigital still camera, a smart phone, a digital photo frame, or a displaydevice in use. That is, the image processing apparatus 1 is used in adevice that displays an image in a display unit, a device that can becoupled with a device having the display unit, or a device that printsor displays an image.

All or a part of processing in the respective processing units (thetable data generation unit 100, the three-dimensional lookup table unit200, the picture adaptation unit 300, the selector 400, the color spacetransformation unit 500) within the image processing apparatus 1 can beconfigured by hardware using a circuit. Further, all or a part ofprocessing in the respective processing units (the table data generationunit 100, the three-dimensional lookup table unit 200, the pictureadaptation unit 300, the selector 400, the color space transformationunit 500) within the image processing apparatus 1 may be realized as aprogram that operates within an arbitrary computer. The program can bestored in a non-transitory computer readable medium of various types,and supplied to the computer. The non-transitory computer readablemedium includes a tangible storage medium of various types. Thenon-transitory computer readable medium is exemplified by a magneticrecording medium (for example, a flexible disc, a magnetic tape, a harddisc drive), a magneto-optical medium (for example, a magneto-opticaldisc), a CD-ROM (read only memory), a CD-R, a CD-R/W, and asemiconductor memory (for example, a mask ROM, a PROM (programmableROM), an EPROM (erasable PROM), a flash ROM, a RAM (random accessmemory)). Also, the program may be supplied to the computer by atransitory computer readable medium of various types. The transitorycomputer readable medium is exemplified by an electric signal, anoptical signal, and an electromagnetic wave. The transitory computerreadable medium can supply the program to the computer through a wiredcommunication path such as an electric wire or an optical fiber, or awireless communication path.

An example of a hardware configuration of a computer which executes theprocessing of the respective processing units in the image processingapparatus 1 as the program is illustrated in FIG. 25. The computerincludes a central processing unit (CPU) 600 and a memory 610. The CPU600 and the memory 610 are coupled to a hard disc device (HDD) 620 as anauxiliary storage device through a bus. An instruction is supplied tothe CPU 600 in cooperation with an operating system so that a computerprogram for implementing the respective processing of theabove-mentioned image processing apparatus 1 can be stored in a storagemedium such as the hard disc device 620.

What is claimed is:
 1. An image processing apparatus, comprising: atransformation unit that transforms color information on an input imagesignal on the basis of a transformation rule; a correction rangecalculation unit that calculates a correction range in a predeterminedcolor space on the basis of a positional relationship between sourcecoordinates and destination coordinates in the color space; and apoint-based transfer distance calculation unit that calculatestransformation destination coordinates at respective points within thecorrection range on the basis of the positional relationship between thesource coordinates and the destination coordinates, and a positionalrelationship between coordinates at the respective points within thecorrection range and the source coordinates to reflect the calculatedtransformation destination coordinates on the transformation rule. 2.The image processing apparatus according to claim 1, wherein thepoint-based transfer distance calculation unit makes the transferdistance at each point smaller as a distance from the source coordinatesis larger.
 3. The image processing apparatus according to claim 1,wherein the correction range comprises an oval sphere in which a firstline connecting the source coordinates and the destination coordinatesis parallel to a long-axis direction.
 4. The image processing apparatusaccording to claim 3, wherein the correction range calculation unitincludes: a first distance calculation unit that calculates a distancebetween the source coordinates and the destination coordinates; a lineinclination calculation unit that calculates an inclination of the firstline; a correction range adjustment unit that calculates the coordinaterange on the basis of a predetermined adjustment value and the distancecalculated by the first distance calculation unit; a rotation anglecalculation unit that calculates a rotation angle by which thecoordinate range is rotated, on the basis of the inclination of thefirst line which is calculated by the line inclination calculation unit;and a correction range oval sphere expression calculation unit thatcalculates the oval sphere by rotating the coordinate range calculatedby the correction range adjustment unit by the rotation angle.
 5. Theimage processing apparatus according to claim 4, wherein the correctionrange calculation unit calculates an inclination Δ1 of a firstcross-section and an inclination Δ2 of a second cross-section of thefirst line in the color space by the following expressions (Ex. 36) and(Ex. 37) when it is assumed that the source coordinates are O(Ro, Go,Bo), and the destination coordinates are T(Rt, Gt, Bt) in the colorspace $\begin{matrix}{{\Delta\; 1} = \frac{{Gt} - {Go}}{{Rt} - {Ro}}} & ( {{Ex}.\mspace{14mu} 36} ) \\{{\Delta\; 2} = {\frac{{Bt} - {Bo}}{{Gt} - {Go}}.}} & ( {{Ex}.\mspace{14mu} 37} )\end{matrix}$
 6. The image processing apparatus according to claim 5,wherein the rotation angle calculation unit calculates the rotationangle θ1 on the first cross-section and the rotation angle θ2 on thesecond cross-section in the color space by the following expressions(Ex. 38) and (Ex. 39) $\begin{matrix}{{{{\theta\; 1} = {\frac{{{atan}( {\Delta\; 1} )} \times 180}{\pi}({^\circ})}},{{{Rt} - {Ro}} = {0\mspace{14mu}{at}\mspace{20mu} 90({^\circ})}}}{{{{where}\mspace{14mu}\theta\; 1\mspace{14mu}{is}\mspace{14mu} 90({^\circ})\mspace{14mu}{if}\mspace{14mu}{Rt}} - {Ro}} = 0}} & ( {{Ex}.\mspace{14mu} 38} ) \\{{{{\theta\; 2} = {\frac{{{atan}( {\Delta\; 2} )} \times 180}{\pi}({^\circ})}},{{{Gt} - {Go}} = {0\mspace{14mu}{at}\mspace{20mu} 0({^\circ})}}}{{{{where}\mspace{14mu}\theta\; 2\mspace{14mu}{is}\mspace{14mu} 0({^\circ})\mspace{14mu}{if}\mspace{14mu}{Gt}} - {Go}} = 0.}} & ( {{Ex}.\mspace{14mu} 39} )\end{matrix}$
 7. The image processing apparatus according to claim 3,wherein the point-based transfer distance calculation unit includes: alinear expression calculation unit that calculates a linear expressionof a second line connecting a first coordinate point included in thecorrection range and the source coordinates; an intersection pointcalculation unit that calculates an intersection point between the ovalsphere and the second line on the basis of a mathematical expression ofthe oval sphere and the linear expression of the second line; a seconddistance calculation unit that calculates a distance between the sourcecoordinates and the intersection point; a third distance calculationunit that calculates a distance between the first coordinate point andthe source coordinates; an influence degree calculation unit thatcalculates the degree of influence which is the basis of the transferdistance of the first coordinate point according to a ratio of thedistance calculated by the second distance calculation unit and thedistance calculated by the third distance calculation unit; and acoordinate calculation unit that calculates the transformationdestination coordinates of the first coordinate point on the basis ofthe degree of influence.
 8. The image processing apparatus according toclaim 7, wherein the coordinate calculation unit calculates thetransformation destination coordinates of the first coordinate pointaccording to a correction direction including one of a (compressiondirection and a parallel direction) designated by the user.
 9. The imageprocessing apparatus according to claim 8, wherein the point-basedtransfer distance calculation unit includes a transfer characteristicadjustment unit that calculates transfer characteristics adjusted to beincreased more than a linear change, and sets the transfercharacteristics as a parameter when the coordinate calculation unitcalculates the transformation destination coordinates of the firstcoordinate point.
 10. The image processing apparatus according to claim1, wherein the coordinates of each point within the correction range tobe processed by the point-based transfer distance calculation unitcomprise lattice point coordinates in which all of distances fromadjacent points are equal to each other.
 11. The image processingapparatus according to claim 1, wherein the source coordinates and thedestination coordinates comprise input values designated by the user.12. The image processing apparatus according to claim 1, furthercomprising a picture adaptation unit that receives, from the user, atype of a memory color correction target, a first preset value of thesource coordinates, and a second preset value of the destinationcoordinates related to each memory color correction target to becorrected, determines whether the memory color correction targetdesignated by the user exists within an image configured by the imagesignal, or not, analyzes a color distribution of the image, adjusts atleast one of the first preset value and the second preset value for eachof the correction targets that exist within the image on the basis ofanalysis results of the color distribution in the image, and setsadjusted values to the source coordinates and the destinationcoordinates for each of the memory color correction targets.
 13. Theimage processing apparatus according to claim 12, wherein the pictureadaptation unit includes: a correction target detection unit thatdetects the presence or absence of an object or a background to besubjected to the memory color correction within the image, and adetection area of the memory color correction target within the image; amemory color correction determination unit that compares a detectionresult of the correction target detection unit with the type of thememory color correction target designated by the user to determine thememory color correction target to be conducted; a histogram generationunit that generates a color space histogram of the image; a histogramanalysis unit that calculates a first analysis result related to a colordistribution analysis within the detection area, and a second analysisresult related to a color distribution analysis between the color spacecoordinates indicated by the first preset value and the second presetvalue, on the basis of the color space histogram; and a source anddestination calculation unit that calculates the source coordinates andthe destination coordinates for each of the memory color correctiontargets which exist within the image, on the basis of the memory colorcorrection target determined by the memory color correctiondetermination unit, the first and second analysis results, and the firstand second preset values.
 14. The image processing apparatus accordingto claim 13, wherein the histogram analysis unit sets main colorcoordinates indicative of a main color in the detection area as thefirst analysis result, divides an area between the color spacecoordinates indicated by the first preset value and the second presetvalue into a plurality of areas, determines whether a given number ofpixels or more exist in the respective areas, or not, in order from anarea closer to the first preset value, and sets the existencecoordinates which are representative coordinates of the areas in whichthe given number of pixels or more exist as the second analysis result.15. The image processing apparatus according to claim 14, wherein thesource and destination calculation unit calculates the sourcecoordinates and the destination coordinates by the following expressions(Ex. 40) and (Ex. 41) assuming that the main color coordinates areOC(OCr, OCg, OCb), the existence coordinates are TE(TEr, TEg, TEb), thefirst preset value is OP(OPr, OPg, ORb), the second preset value isTP(TPr, TPg, TRb), the source coordinates are O(Ro, Go, Bo), thedestination coordinates are T(Rt, Gt, Bt), and following degreesadjustable by the user are F1(0˜100%) and F2(0˜100%)Ro=OPr+(OCr−OPr)×F1Go=OPg+(OCg−OPg)×F1Bo=OPb+(OCb−OPb)×F1  (Ex. 40)Rt=TPr+(TEr−TPr)×F2Gt=TPg+(TEg−TEg)×F2Rt=TPr+(TEb−TPb)×F2  (Ex. 41)
 16. The image processing apparatusaccording to claim 1, wherein the correction range calculation unitreceives an input of a rule limit number of the transformation rule fromthe user, compares the number of respective point coordinates within thecorrection range which is calculated from a size of the correction rangewith the rule limit number, and recalculates the correction range sothat the area range becomes smaller if the rule limit number is smallerthan the number of respective dot coordinates within the correctionrange.
 17. The image processing apparatus according to claim 1, whereinthe correction range calculation unit receives an input of a priorityorder of the memory color correction targets from the user, determineswhether the correction ranges of the respective memory color correctiontargets overlap with each other, and recalculates the correction rangesof the respective memory color correction targets so that a reductionratio of the correction ranges of the memory color correction targetsbecomes larger in ascending order of the priority order.
 18. The imageprocessing apparatus according to claim 16, wherein the correction rangecalculation unit recalculates the correction ranges after at least oneof the source coordinates and the destination coordinates is so adjustedas to decrease a distance between the source coordinates and thedestination coordinates.
 19. The image processing apparatus according toclaim 13, wherein the transformation unit includes at least a firsttransformation unit and a second transformation unit, wherein thepicture adaptation unit detects the respective display areas of thefirst color correction target and the second memory color correctiontarget, which are the memory color correction targets designated by theuser, within the image, wherein the correction range calculation unitcalculates the respective correction ranges corresponding to the firstand second memory color correction targets, and wherein the point-basedtransfer distance calculation unit calculates the transformationdestination coordinates of the respective points within the correctionrange of the first memory color correction target to reflect thecalculated transformation destination coordinates on the transformationrule of the first transformation unit, and calculates the transformationdestination coordinates of the respective points within the correctionrange of the second memory color correction target to reflect thecalculated transformation destination coordinates on the transformationrule of the second transformation unit.
 20. The image processingapparatus according to claim 1, wherein the color space comprises anyone of RGB, HSV, HSU, YUV, HLS, Lab, and YCM.
 21. The image processingapparatus according to claim 1, wherein the transformation rulecomprises an LUT (lookup table).
 22. An image processing method oftransforming color information on an input image signal on the basis ofa transformation rule, comprising: calculating a correction range in apredetermined color space on the basis of a positional relationshipbetween source coordinates and destination coordinates in the colorspace; and calculating transformation destination coordinates atrespective points within the correction range on the basis of thepositional relationship between the source coordinates and thedestination coordinates, and a positional relationship betweencoordinates at the respective points within the correction range and thesource coordinates to reflect the calculated transformation destinationcoordinates on the transformation rule.
 23. A non-transitory computerreadable recording medium storing a program causing a computer toexecute processing comprising: transforming color information on aninput image signal on the basis of a transformation rule; calculating acorrection range in a predetermined color space on the basis of apositional relationship between source coordinates and destinationcoordinates in the color space; and calculating transformationdestination coordinates at respective points within the correction rangeon the basis of the positional relationship between the sourcecoordinates and the destination coordinates, and a positionalrelationship between coordinates at the respective points within thecorrection range and the source coordinates to reflect the calculatedtransformation destination coordinates on the transformation rule.